Bump mkdocs-material from 9.6.20 to 9.6.21 in the dependencies group (#1157)

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


Updates `mkdocs-material` from 9.6.20 to 9.6.21
- [Release notes](https://github.com/squidfunk/mkdocs-material/releases)
- [Changelog](https://github.com/squidfunk/mkdocs-material/blob/master/CHANGELOG)
- [Commits](squidfunk/mkdocs-material@9.6.20...9.6.21)

---
updated-dependencies:
- dependency-name: mkdocs-material
  dependency-version: 9.6.21
  dependency-type: direct:production
  update-type: version-update:semver-patch
  dependency-group: dependencies
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

requirements.txt

@@ -1,4 +1,4 @@
 mkdocs==1.6.1
 mkdocs-codeinclude-plugin==0.2.1
 mkdocs-markdownextradata-plugin==0.2.6
-mkdocs-material==9.6.20
+mkdocs-material==9.6.22