Removed reference to GCP gym registry. (Unity-Technologies#6107)

Author: miguelalonsojr

ml-agents-envs/mlagents_envs/registry/unity_env_registry.py

@@ -120,6 +120,7 @@ def __iter__(self) -> Iterator[Any]:
 
 
 default_registry = UnityEnvRegistry()
-default_registry.register_from_yaml(
-    "https://storage.googleapis.com/mlagents-test-environments/1.1.0/manifest.yaml"
-)  # noqa E501
+# TODO restore when a new registry is available.
+# default_registry.register_from_yaml(
+#     "https://storage.googleapis.com/mlagents-test-environments/1.1.0/manifest.yaml"
+# )  # noqa E501