Add back error message unconditionally

.github/workflows/staleness_check.yml

@@ -53,6 +53,7 @@ jobs:
         # commit.
         run: |
           set -ex
+          echo "Please run ./regenerate_stale_files.sh to regenerate stale files";
           if [[ -z $COMMIT_TRIGGERED_RUN || -z $MAIN_RUN ]]; then
             bazel query 'attr(tags, "staleness_test", //...)' | xargs bazel test $BAZEL_FLAGS
           else