Disable issue generation for FirebasePrivate repo. (#7055)

Author: granluo

.github/workflows/generate_issues.yml

@@ -5,6 +5,8 @@ on:
     - cron:  '0 13 * * *'
 jobs:
   generate_an_issue:
+    # Don't run on private repo.
+    if: github.repository == 'Firebase/firebase-ios-sdk' && github.event_name == 'schedule'
     runs-on: ubuntu-latest
     name: Generate a nightly testing report issue
     steps: