Make pull_request.yaml between the layers consistent and fix enforce labels (#8580)

.github/workflows/pull_request.yaml

@@ -1,10 +1,11 @@
 name: Pull Request
 on:
   pull_request_target:
-    types: [ opened, edited, labeled, unlabeled ]
+    types: [ opened, edited, labeled, unlabeled, synchronize ]
 jobs:
   changelog:
     name: Preview Changelog
+    if: github.event.action != 'synchronize'
     runs-on: ubuntu-latest
     steps:
       - uses: matrix-org/allchange@main