ci: declare explicit permissions in maintenance workflows (#38159)

Co-authored-by: rohan436 <rohan.santhoshkumar@googlemail.com>

.github/workflows/pre-commit.yml

@@ -8,6 +8,9 @@ on:
   pull_request:
     types: [synchronize, opened, reopened, ready_for_review]
 
+permissions:
+  contents: read
+
 # cancel previous workflow jobs for PRs
 concurrency:
   group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.run_id }}