CI: auto-merge: rebase again before push

(cherry picked from commit 9b858b2)

Author: ting-yuan

.github/workflows/auto-merge.yml

@@ -88,7 +88,7 @@ jobs:
 
       - name: push to release branch
         if: success()
-        run: git push origin
+        run: git fetch && git rebase && git push origin
 
       - name: Upload test results
         if: always()