build(deps): bump zeebe-io/backport-action from 1.4.0 to 2.1.0

Bumps [zeebe-io/backport-action](https://github.com/zeebe-io/backport-action) from 1.4.0 to 2.1.0.
- [Release notes](https://github.com/zeebe-io/backport-action/releases)
- [Commits](korthout/backport-action@v1.4.0...v2.1.0)

---
updated-dependencies:
- dependency-name: zeebe-io/backport-action
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/back-port.yaml

@@ -30,7 +30,7 @@ jobs:
         with:
           fetch-depth: 0
       - name: Create Backport PR
-        uses: zeebe-io/backport-action@v1.4.0
+        uses: zeebe-io/backport-action@v2.1.0
         with:
           github_token: ${{ secrets.GITHUB_TOKEN }}
           github_workspace: ${{ github.workspace }}