Bump zeebe-io/backport-action from 1.3.1 to 1.4.0

Bumps [zeebe-io/backport-action](https://github.com/zeebe-io/backport-action) from 1.3.1 to 1.4.0.
- [Release notes](https://github.com/zeebe-io/backport-action/releases)
- [Commits](https://github.com/zeebe-io/backport-action/compare/v1.3.1...v1.4.0)

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

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/backport.yml

@@ -21,7 +21,7 @@ jobs:
           fetch-depth: 0
       - name: Create backport PRs
         # should be kept in sync with `version`
-        uses: zeebe-io/backport-action@v1.3.1
+        uses: zeebe-io/backport-action@v1.4.0
         with:
           # Config README: https://github.com/zeebe-io/backport-action#backport-action
           github_token: ${{ secrets.GITHUB_TOKEN }}