build(deps-dev): bump mkdocs-material from 9.0.11 to 9.1.6

Bumps [mkdocs-material](https://github.com/squidfunk/mkdocs-material) from 9.0.11 to 9.1.6.
- [Release notes](https://github.com/squidfunk/mkdocs-material/releases)
- [Changelog](https://github.com/squidfunk/mkdocs-material/blob/master/CHANGELOG)
- [Commits](squidfunk/mkdocs-material@9.0.11...9.1.6)

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

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