Try fixing contributor PR notice (#2335)

* Try fixing contributor PR notice

.github/workflows/fork-pr-notice.yml

@@ -11,7 +11,8 @@ jobs:
   welcome:
     runs-on: ubuntu-latest
     name: Welcome comment
-    if: github.event.pull_request.fork != null
+    # Only display it if base repo (upstream) is different from HEAD repo (possibly a fork)
+    if: github.event.pull_request.base.repo.full_name != github.event.pull_request.head.repo.full_name
     steps:
       - name: Add auto-generated commit warning
         uses: actions/github-script@v7