pin to version v0.13.1

Author: basnijholt

.github/workflows/automerge.yml

@@ -22,7 +22,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: automerge
-        uses: "pascalgn/automerge-action@f81beb99aef41bb55ad072857d43073fba833a98"
+        uses: "pascalgn/automerge-action@v0.13.1"
         env:
           GITHUB_TOKEN: "${{ secrets.GITHUB_TOKEN }}"
           MERGE_LABELS: "automerge"