fix backport shows generic error when conflicts (#24928)

.github/workflows/auto-backport.yml

@@ -67,12 +67,14 @@ jobs:
           COMMIT: ${{ steps.find_commit.outputs.commit }}
 
       - name: Auto approve backport PR
+        if: ${{ steps.create_backport_pull_request.outputs.has-conflicts == 'false' }}
         uses: juliangruber/approve-pull-request-action@v1
         with:
           github-token: ${{ secrets.GITHUB_TOKEN }}
           number: ${{ steps.create_backport_pull_request.outputs.backport_pr_number }}
 
       - name: Enable Pull Request Automerge
+        if: ${{ steps.create_backport_pull_request.outputs.has-conflicts == 'false' }}
         uses: peter-evans/enable-pull-request-automerge@v2
         with:
           token: ${{ steps.generate-token.outputs.token }}