dependabot: use DEPENDABOT_TOKEN for push

Author: rsteube

.github/workflows/dependabot.yml

@@ -29,8 +29,10 @@ jobs:
           git config user.email rsteube-bot@users.noreply.github.com
           git add -A
           git commit -m "updated botocore"
-          git push https://rsteube-bot:${GITHUB_TOKEN}@github.com/carapace-sh/carapace-aws.git HEAD:${GITHUB_HEAD_REF}
+          git push https://rsteube-bot:${DEPENDABOT_TOKEN}@github.com/carapace-sh/carapace-aws.git HEAD:${GITHUB_HEAD_REF}
         fi
+        env:
+          DEPENDABOT_TOKEN: ${{ secrets.DEPENDABOT_TOKEN }}
 
   auto-merge:
     runs-on: ubuntu-latest