build(deps): bump mkdocs-git-authors-plugin from 0.8.0 to 0.9.0 in /docs

Bumps [mkdocs-git-authors-plugin](https://github.com/timvink/mkdocs-git-authors-plugin) from 0.8.0 to 0.9.0.
- [Release notes](https://github.com/timvink/mkdocs-git-authors-plugin/releases)
- [Commits](timvink/mkdocs-git-authors-plugin@v0.8.0...v0.9.0)

---
updated-dependencies:
- dependency-name: mkdocs-git-authors-plugin
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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