chore: update .repo-metadata.json (#50)

Author: parthea

.repo-metadata.json

@@ -3,12 +3,13 @@
     "name_pretty": "Source Context",
     "client_documentation": "https://cloud.google.com/python/docs/reference/source/latest",
     "issue_tracker": "http://github.com/googleapis/python-source-context/issues",
-    "release_level": "ga",
+    "release_level": "stable",
     "language": "python",
     "library_type": "GAPIC_AUTO",
     "repo": "googleapis/python-source-context",
     "distribution_name": "google-cloud-source-context",
     "api_id": "source.googleapis.com",
     "default_version": "v1",
-    "codeowner_team": ""
+    "codeowner_team": "",
+    "api_shortname": "source"
 }