Update pascalgn/automerge-action action to v0.15.5

Author: renovate[bot]

.github/workflows/auto-merge.yml

@@ -29,7 +29,7 @@ jobs:
     steps:
       - id: automerge
         name: automerge
-        uses: pascalgn/automerge-action@v0.15.3
+        uses: pascalgn/automerge-action@v0.15.5
         env:
           GITHUB_TOKEN: '${{ secrets.GITHUB_TOKEN }}'
           MERGE_LABELS: 'dependencies'