update repo-metadata file

Author: ohmayr

packages/gapic-generator/.repo-metadata.json

@@ -3,7 +3,7 @@
     "name_pretty": "Google API Client Generator for Python",
     "client_documentation": "https://gapic-generator-python.readthedocs.io/en/stable/",
     "product_documentation": "",
-    "issue_tracker": "https://github.com/googleapis/gapic-generator-python/issues",
+    "issue_tracker": "https://github.com/googleapis/google-cloud-python/issues",
     "release_level": "stable",
     "language": "python",
     "library_type": "CORE",