chore: Add api_id to repo-metadata.json of grafeas (#10831)

The value is copied from the [service yaml](name: containeranalysis.googleapis.com) of grafeas.

java-grafeas/.repo-metadata.json

@@ -10,7 +10,7 @@
     "repo": "googleapis/google-cloud-java",
     "repo_short": "java-grafeas",
     "distribution_name": "io.grafeas:grafeas",
-    "api_id": "",
+    "api_id": "containeranalysis.googleapis.com",
     "codeowner_team": "@googleapis/aap-dpes",
     "library_type": "GAPIC_AUTO"
 }