chore: enable librarian "generation" for gapic-generator (googleapis#16728)

Author: jskeet

librarian.yaml

@@ -92,7 +92,6 @@ libraries:
       issue_tracker_override: https://issuetracker.google.com/issues?q=componentid:190851%2B%20status:open
   - name: gapic-generator
     version: 1.30.14
-    skip_generate: true
     python:
       library_type: CORE
       name_pretty_override: Google API Client Generator for Python

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

@@ -1,14 +1,11 @@
 {
-    "name": "gapic-generator",
-    "name_pretty": "Google API Client Generator for Python",
     "client_documentation": "https://gapic-generator-python.readthedocs.io/en/stable/",
-    "product_documentation": "",
+    "distribution_name": "gapic-generator",
     "issue_tracker": "https://github.com/googleapis/google-cloud-python/issues",
-    "release_level": "stable",
     "language": "python",
     "library_type": "CORE",
-    "repo": "googleapis/google-cloud-python",
-    "distribution_name": "gapic-generator",
-    "default_version": "",
-    "codeowner_team": "@googleapis/cloud-sdk-python-team"
-}
+    "name": "gapic-generator",
+    "name_pretty": "Google API Client Generator for Python",
+    "release_level": "stable",
+    "repo": "googleapis/google-cloud-python"
+}