ci: Fail FM Sync

.github/workflows/follow-merge-sync-pr.yml

@@ -58,6 +58,7 @@ jobs:
                 `Unfortunately you don't have membership in ${owner} organization, your PR wasn't synced with ${owner}/${{ env.DOWNSTREAM_REPOSITORY }}.`
               ].join('\n')
             });
+            throw `${{ github.actor }} don't have membership in ${owner} organization`
 
       - name: Checkout Actions Hub
         uses: actions/checkout@v4