chore(deps-dev): bump the all-dependencies group with 2 updates (#454)

Bumps the all-dependencies group with 2 updates: [mkdocs](https://github.com/mkdocs/mkdocs) and [mkdocs-material](https://github.com/squidfunk/mkdocs-material).


Updates `mkdocs` from 1.5.0 to 1.5.1
- [Release notes](https://github.com/mkdocs/mkdocs/releases)
- [Commits](mkdocs/mkdocs@1.5.0...1.5.1)

Updates `mkdocs-material` from 9.1.20 to 9.1.21
- [Release notes](https://github.com/squidfunk/mkdocs-material/releases)
- [Changelog](https://github.com/squidfunk/mkdocs-material/blob/master/CHANGELOG)
- [Commits](squidfunk/mkdocs-material@9.1.20...9.1.21)

---
updated-dependencies:
- dependency-name: mkdocs
  dependency-type: direct:development
  update-type: version-update:semver-patch
  dependency-group: all-dependencies
- dependency-name: mkdocs-material
  dependency-type: direct:development
  update-type: version-update:semver-patch
  dependency-group: all-dependencies
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>