Update auto-approve.yml

Author: dimafeng

.github/workflows/auto-approve.yml

@@ -7,6 +7,7 @@ jobs:
     steps:
       - name: automerge
         uses: "pascalgn/[email protected]"
+        if: github.actor == 'scala-steward'
         env:
           GITHUB_TOKEN: "${{ secrets.GITHUB_TOKEN }}"
           MERGE_LABELS: ""