ci: update auto merge action version to latest

Author: kagawagao

.github/workflows/automerge.yml

@@ -22,7 +22,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: automerge
-        uses: "pascalgn/automerge-action@v0.12.0"
+        uses: "pascalgn/automerge-action@latest"
         env:
           GITHUB_TOKEN: "${{ secrets.GITHUB_TOKEN }}"
           MERGE_LABELS: "dependencies,!wip"