ci(sync): skip main repo execution

.github/workflows/sync.yml

@@ -9,6 +9,7 @@ jobs:
   sync_latest_from_upstream:
     name: Sync latest commits from upstream repo
     runs-on: ubuntu-latest
+    if: ${{ github.event.repository.fork }}
 
     steps:
       # Step 1: run a standard checkout action, provided by github