Potential fix for code scanning alert no. 3: Workflow does not contain permissions (#4273)

Co-authored-by: Copilot Autofix powered by AI <62310815+github-advanced-security[bot]@users.noreply.github.com>

Author: jiaren-wu

.github/workflows/arc-update-runners-scheduled.yaml

@@ -50,6 +50,8 @@ jobs:
   # it sets a PR name as output.
   check_pr:
     runs-on: ubuntu-latest
+    permissions:
+      contents: read
     needs: check_versions
     if: needs.check_versions.outputs.runner_current_version != needs.check_versions.outputs.runner_latest_version || needs.check_versions.outputs.container_hooks_current_version != needs.check_versions.outputs.container_hooks_latest_version
     outputs: