dependabot: try just gh pr merge

Author: mistydemeo

.github/workflows/dependabot.yml

@@ -40,7 +40,6 @@ jobs:
           PR_URL: ${{ github.event.pull_request.html_url }}
           GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
       - name: Merge PR
-        run: gh pr merge "$PR_URL"
+        run: gh pr merge
         env:
-          PR_URL: ${{ github.event.pull_request.html_url }}
           GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}