ci: fix token in backend update workflow

.github/workflows/update_backend.yml

@@ -40,7 +40,6 @@ jobs:
       - name: "Create PR if necessary"
         uses: peter-evans/create-pull-request@v6
         with:
-          token: ${{ secrets.REPO_SCOPED_TOKEN }}
           title: "Automated update to backend: v${{ steps.get-latest.outputs.version }}"
           body: |
             This PR was automatically generated by the GitHub Action `.github/workflows/update-backend.yml`