ci: trigger auto merge only when succeed

Author: Brooooooklyn

.github/workflows/auto-merge.yaml

@@ -15,6 +15,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Auto merge
+        if: ${{ github.event.workflow_run.conclusion == 'success' }}
         uses: ridedott/merge-me-action@v2
         with:
           GITHUB_LOGIN: 'dependabot*'