build(deps): bump mkdocs-material in /docs in the docs group

Bumps the docs group in /docs with 1 update: [mkdocs-material](https://github.com/squidfunk/mkdocs-material).


Updates `mkdocs-material` from 9.6.1 to 9.6.6
- [Release notes](https://github.com/squidfunk/mkdocs-material/releases)
- [Changelog](https://github.com/squidfunk/mkdocs-material/blob/master/CHANGELOG)
- [Commits](squidfunk/mkdocs-material@9.6.1...9.6.6)

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

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

Author: dependabot[bot]