chore: [docs] Update mkdocs-material requirement in /docs

Updates the requirements on [mkdocs-material](https://github.com/squidfunk/mkdocs-material) to permit the latest version.
- [Release notes](https://github.com/squidfunk/mkdocs-material/releases)
- [Changelog](https://github.com/squidfunk/mkdocs-material/blob/master/CHANGELOG)
- [Commits](squidfunk/mkdocs-material@9.4.5...9.4.6)

---
updated-dependencies:
- dependency-name: mkdocs-material
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

docs/requirements.txt

@@ -1,4 +1,4 @@
 mkdocs ~= 1.5.3
-mkdocs-material ~= 9.4.5
+mkdocs-material ~= 9.4.6
 mkdocs-material-extensions ~= 1.2
 mkdocs-redirects ~= 1.2.1