update: update mkdocs-material requirement from ~=8.2.9 to ~=8.2.11

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@8.2.9...8.2.11)

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

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

docs/requirements_docs.txt

@@ -1,2 +1,2 @@
-mkdocs-material~=8.2.9
+mkdocs-material~=8.2.11
 mike~=1.1.2