Bump mkdocs-material from 7.3.6 to 8.1.9

Bumps [mkdocs-material](https://github.com/squidfunk/mkdocs-material) from 7.3.6 to 8.1.9.
- [Release notes](https://github.com/squidfunk/mkdocs-material/releases)
- [Changelog](https://github.com/squidfunk/mkdocs-material/blob/master/CHANGELOG)
- [Upgrade guide](https://github.com/squidfunk/mkdocs-material/blob/master/docs/upgrade.md)
- [Commits](squidfunk/mkdocs-material@7.3.6...8.1.9)

---
updated-dependencies:
- dependency-name: mkdocs-material
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

docs/requirements.txt

@@ -1,6 +1,6 @@
 mkdocs==1.2.3
 mkdocs-autorefs==0.3.0
 mkdocs-awesome-pages-plugin==2.6.0
-mkdocs-material==7.3.6
+mkdocs-material==8.1.9
 mkdocs-material-extensions==1.0.3
 mkdocstrings==0.16.2