refactor: bump @saithodev/semantic-release-backmerge from 2.1.3 to 3.2.1

Bumps [@saithodev/semantic-release-backmerge](https://github.com/saitho/semantic-release-backmerge) from 2.1.3 to 3.2.1.
- [Release notes](https://github.com/saitho/semantic-release-backmerge/releases)
- [Changelog](https://github.com/saitho/semantic-release-backmerge/blob/master/CHANGELOG.md)
- [Commits](saitho/semantic-release-backmerge@v2.1.3...v3.2.1)

---
updated-dependencies:
- dependency-name: "@saithodev/semantic-release-backmerge"
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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