configure PAT for automerge

Author: swissiety

.github/workflows/approve_dependabotifications.yml

@@ -22,4 +22,4 @@ jobs:
         run: gh pr merge --auto --merge "$PR_URL"
         env:
           PR_URL: ${{github.event.pull_request.html_url}}
-          GH_TOKEN: ${{secrets.GITHUB_TOKEN}}
+          GH_TOKEN: ${{secrets.PAT_AUTO_MERGE}}