build(deps): bump korthout/backport-action from 2.0.0 to 2.1.0

Bumps [korthout/backport-action](https://github.com/korthout/backport-action) from 2.0.0 to 2.1.0.
- [Release notes](https://github.com/korthout/backport-action/releases)
- [Commits](https://github.com/korthout/backport-action/compare/v2.0.0...v2.1.0)

---
updated-dependencies:
- dependency-name: korthout/backport-action
dependency-type: direct:production
update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[e-mail]>

.github/workflows/backport.yml

···
         with:
           ref: ${{ github.event.pull_request.head.sha }}
       - name: Create backport PRs
-        uses: korthout/backport-action@v2.0.0
+        uses: korthout/backport-action@v2.1.0
         with:
           # Config README: https://github.com/korthout/backport-action#backport-action
           copy_labels_pattern: 'severity:\ssecurity'