Update workflow

Author: peter-evans

.github/workflows/automerge-dependabot.yml

@@ -1,17 +1,13 @@
 name: Auto-merge Dependabot
 on: pull_request
 
-permissions:
-  pull-requests: write
-  contents: write
-
 jobs:
   automerge:
     runs-on: ubuntu-latest
     if: github.actor == 'dependabot[bot]'
     steps:
       - uses: peter-evans/enable-pull-request-automerge@v2
         with:
-          token: ${{ secrets.GITHUB_TOKEN }}
+          token: ${{ secrets.DEPENDABOT_AUTOMERGE }}
           pull-request-number: ${{ github.event.pull_request.number }}
           merge-method: squash