Bump mkdocs-material from 9.2.6 to 9.2.8

Bumps [mkdocs-material](https://github.com/squidfunk/mkdocs-material) from 9.2.6 to 9.2.8.
- [Release notes](https://github.com/squidfunk/mkdocs-material/releases)
- [Changelog](https://github.com/squidfunk/mkdocs-material/blob/master/CHANGELOG)
- [Commits](squidfunk/mkdocs-material@9.2.6...9.2.8)

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

Signed-off-by: dependabot[bot] <[email protected]>