ci: bump korthout/backport-action from 4.1.0 to 4.3.0

Bumps [korthout/backport-action](https://github.com/korthout/backport-action) from 4.1.0 to 4.3.0.
- [Release notes](https://github.com/korthout/backport-action/releases)
- [Commits](https://github.com/korthout/backport-action/compare/v4.1.0...v4.3.0)

---
updated-dependencies:
- dependency-name: korthout/backport-action
  dependency-version: 4.3.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
(cherry picked from commit d27951a653)

.github/workflows/backport.yml

@@ -45,7 +45,7 @@ jobs:
           ref: ${{ github.event.pull_request.head.sha }}
           token: ${{ steps.app-token.outputs.token }}
 
-      - uses: korthout/backport-action@v4.1.0
+      - uses: korthout/backport-action@v4.3.0
         id: backport
         with:
           github_token: ${{ steps.app-token.outputs.token }}