chore: clean up HAS_GRPC_GCP (#892)

diff --git a/google/api_core/grpc_helpers.py b/google/api_core/grpc_helpers.py
index b135364..30ba19c 100644
--- a/google/api_core/grpc_helpers.py
+++ b/google/api_core/grpc_helpers.py
@@ -27,8 +27,6 @@
 
 from google.api_core import exceptions, general_helpers
 
-HAS_GRPC_GCP = False
-
 
 # The list of gRPC Callable interfaces that return iterators.
 _STREAM_WRAP_CLASSES = (grpc.UnaryStreamMultiCallable, grpc.StreamStreamMultiCallable)
diff --git a/tests/unit/test_grpc_helpers.py b/tests/unit/test_grpc_helpers.py
index ed4a922..e05d396 100644
--- a/tests/unit/test_grpc_helpers.py
+++ b/tests/unit/test_grpc_helpers.py
@@ -404,16 +404,9 @@
 
     google_auth_default.assert_called_once_with(scopes=None, default_scopes=None)
 
-    if grpc_helpers.HAS_GRPC_GCP:  # pragma: NO COVER
-        # The original target is the expected target
-        expected_target = target
-        grpc_secure_channel.assert_called_once_with(
-            expected_target, composite_creds, None
-        )
-    else:
-        grpc_secure_channel.assert_called_once_with(
-            expected_target, composite_creds, compression=grpc.Compression.Gzip
-        )
+    grpc_secure_channel.assert_called_once_with(
+        expected_target, composite_creds, compression=grpc.Compression.Gzip
+    )
 
 
 @pytest.mark.parametrize(
@@ -463,16 +456,9 @@
         mock.sentinel.credentials, mock.sentinel.Request, default_host=default_host
     )
 
-    if grpc_helpers.HAS_GRPC_GCP:  # pragma: NO COVER
-        # The original target is the expected target
-        expected_target = target
-        grpc_secure_channel.assert_called_once_with(
-            expected_target, composite_creds, None
-        )
-    else:
-        grpc_secure_channel.assert_called_once_with(
-            expected_target, composite_creds, compression=None
-        )
+    grpc_secure_channel.assert_called_once_with(
+        expected_target, composite_creds, compression=None
+    )
 
 
 @pytest.mark.parametrize(
@@ -505,12 +491,9 @@
     composite_creds_call.assert_called_once_with(ssl_creds, mock.ANY)
     composite_creds = composite_creds_call.return_value
 
-    if grpc_helpers.HAS_GRPC_GCP:  # pragma: NO COVER
-        grpc_secure_channel.assert_called_once_with(target, composite_creds, None)
-    else:
-        grpc_secure_channel.assert_called_once_with(
-            target, composite_creds, compression=None
-        )
+    grpc_secure_channel.assert_called_once_with(
+        target, composite_creds, compression=None
+    )
 
 
 def test_create_channel_implicit_with_ssl_creds_attempt_direct_path_true():
@@ -543,12 +526,9 @@
 
     default.assert_called_once_with(scopes=["one", "two"], default_scopes=None)
 
-    if grpc_helpers.HAS_GRPC_GCP:  # pragma: NO COVER
-        grpc_secure_channel.assert_called_once_with(target, composite_creds, None)
-    else:
-        grpc_secure_channel.assert_called_once_with(
-            target, composite_creds, compression=None
-        )
+    grpc_secure_channel.assert_called_once_with(
+        target, composite_creds, compression=None
+    )
 
 
 @mock.patch("grpc.compute_engine_channel_credentials")
@@ -570,12 +550,9 @@
 
     default.assert_called_once_with(scopes=None, default_scopes=["three", "four"])
 
-    if grpc_helpers.HAS_GRPC_GCP:  # pragma: NO COVER
-        grpc_secure_channel.assert_called_once_with(target, composite_creds, None)
-    else:
-        grpc_secure_channel.assert_called_once_with(
-            target, composite_creds, compression=None
-        )
+    grpc_secure_channel.assert_called_once_with(
+        target, composite_creds, compression=None
+    )
 
 
 def test_create_channel_explicit_with_duplicate_credentials():
@@ -605,12 +582,9 @@
 
     assert channel is grpc_secure_channel.return_value
 
-    if grpc_helpers.HAS_GRPC_GCP:  # pragma: NO COVER
-        grpc_secure_channel.assert_called_once_with(target, composite_creds, None)
-    else:
-        grpc_secure_channel.assert_called_once_with(
-            target, composite_creds, compression=None
-        )
+    grpc_secure_channel.assert_called_once_with(
+        target, composite_creds, compression=None
+    )
 
 
 @mock.patch("grpc.compute_engine_channel_credentials")
@@ -631,12 +605,9 @@
 
     assert channel is grpc_secure_channel.return_value
 
-    if grpc_helpers.HAS_GRPC_GCP:  # pragma: NO COVER
-        grpc_secure_channel.assert_called_once_with(target, composite_creds, None)
-    else:
-        grpc_secure_channel.assert_called_once_with(
-            target, composite_creds, compression=None
-        )
+    grpc_secure_channel.assert_called_once_with(
+        target, composite_creds, compression=None
+    )
 
 
 @mock.patch("grpc.compute_engine_channel_credentials")
@@ -661,12 +632,9 @@
 
     assert channel is grpc_secure_channel.return_value
 
-    if grpc_helpers.HAS_GRPC_GCP:  # pragma: NO COVER
-        grpc_secure_channel.assert_called_once_with(target, composite_creds, None)
-    else:
-        grpc_secure_channel.assert_called_once_with(
-            target, composite_creds, compression=None
-        )
+    grpc_secure_channel.assert_called_once_with(
+        target, composite_creds, compression=None
+    )
 
 
 @mock.patch("grpc.compute_engine_channel_credentials")
@@ -689,12 +657,9 @@
 
     assert channel is grpc_secure_channel.return_value
 
-    if grpc_helpers.HAS_GRPC_GCP:  # pragma: NO COVER
-        grpc_secure_channel.assert_called_once_with(target, composite_creds, None)
-    else:
-        grpc_secure_channel.assert_called_once_with(
-            target, composite_creds, compression=None
-        )
+    grpc_secure_channel.assert_called_once_with(
+        target, composite_creds, compression=None
+    )
 
 
 @mock.patch("grpc.compute_engine_channel_credentials")
@@ -721,12 +686,9 @@
 
     assert channel is grpc_secure_channel.return_value
 
-    if grpc_helpers.HAS_GRPC_GCP:  # pragma: NO COVER
-        grpc_secure_channel.assert_called_once_with(target, composite_creds, None)
-    else:
-        grpc_secure_channel.assert_called_once_with(
-            target, composite_creds, compression=None
-        )
+    grpc_secure_channel.assert_called_once_with(
+        target, composite_creds, compression=None
+    )
 
 
 @mock.patch("grpc.compute_engine_channel_credentials")
@@ -756,12 +718,9 @@
 
     assert channel is grpc_secure_channel.return_value
 
-    if grpc_helpers.HAS_GRPC_GCP:  # pragma: NO COVER
-        grpc_secure_channel.assert_called_once_with(target, composite_creds, None)
-    else:
-        grpc_secure_channel.assert_called_once_with(
-            target, composite_creds, compression=None
-        )
+    grpc_secure_channel.assert_called_once_with(
+        target, composite_creds, compression=None
+    )
 
 
 @mock.patch("grpc.compute_engine_channel_credentials")
@@ -791,32 +750,11 @@
 
     assert channel is grpc_secure_channel.return_value
 
-    if grpc_helpers.HAS_GRPC_GCP:  # pragma: NO COVER
-        grpc_secure_channel.assert_called_once_with(target, composite_creds, None)
-    else:
-        grpc_secure_channel.assert_called_once_with(
-            target, composite_creds, compression=None
-        )
+    grpc_secure_channel.assert_called_once_with(
+        target, composite_creds, compression=None
+    )
 
 
[email protected](
-    not grpc_helpers.HAS_GRPC_GCP, reason="grpc_gcp module not available"
-)
[email protected]("grpc_gcp.secure_channel")
-def test_create_channel_with_grpc_gcp(grpc_gcp_secure_channel):  # pragma: NO COVER
-    target = "example.com:443"
-    scopes = ["test_scope"]
-
-    credentials = mock.create_autospec(google.auth.credentials.Scoped, instance=True)
-    credentials.requires_scopes = True
-
-    grpc_helpers.create_channel(target, credentials=credentials, scopes=scopes)
-    grpc_gcp_secure_channel.assert_called()
-
-    credentials.with_scopes.assert_called_once_with(scopes, default_scopes=None)
-
-
[email protected](grpc_helpers.HAS_GRPC_GCP, reason="grpc_gcp module not available")
 @mock.patch("grpc.secure_channel")
 def test_create_channel_without_grpc_gcp(grpc_secure_channel):
     target = "example.com:443"