chore(ci): fallback togithub.token if repo scoped does not exist (#628)

Author: christinewangcw

.github/workflows/pre-commit.yml

@@ -20,7 +20,7 @@ jobs:
           fetch-depth: 0
           repository: ${{ github.event.pull_request.head.repo.full_name }}
           ref: ${{ github.event.pull_request.head.ref }}
-          token: ${{ secrets.REPO_SCOPED_TOKEN }}
+          token: ${{ secrets.REPO_SCOPED_TOKEN || github.token }}
 
       - name: Setup environment
         uses: ./.github/actions/setup-environment