Bump mkdocs-material from 8.3.9 to 8.4.0 (#519)

Bumps [mkdocs-material](https://github.com/squidfunk/mkdocs-material) from 8.3.9 to 8.4.0.
- [Release notes](https://github.com/squidfunk/mkdocs-material/releases)
- [Changelog](https://github.com/squidfunk/mkdocs-material/blob/master/CHANGELOG)
- [Commits](squidfunk/mkdocs-material@8.3.9...8.4.0)

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

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

requirements.txt

@@ -1,2 +1,2 @@
 mkdocs==1.3.1
-mkdocs-material==8.3.9
+mkdocs-material==8.4.0