build(deps): bump korthout/backport-action from 1.2.0 to 1.3.1

Bumps [korthout/backport-action](https://github.com/korthout/backport-action) from 1.2.0 to 1.3.1.
- [Release notes](https://github.com/korthout/backport-action/releases)
- [Commits](https://github.com/korthout/backport-action/compare/v1.2.0...v1.3.1

)

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

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