chore(deps): update mergifyio/gha-mergify-ci action to v21

Author: renovate[bot]

.github/workflows/ci.yaml

@@ -182,7 +182,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Verify all jobs succeeded
-        uses: Mergifyio/gha-mergify-ci@v20
+        uses: Mergifyio/gha-mergify-ci@v21
         with:
           action: wait-jobs
           jobs: ${{ toJSON(needs) }}