Use PUSH_TOKEN for automerge [skip ci]

Author: aivus

.github/workflows/dependabot-automerge.yml

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