chore(deps-dev): bump mkdocs-material from 9.6.14 to 9.6.21 (#280)

Bumps [mkdocs-material](https://github.com/squidfunk/mkdocs-material) from 9.6.14 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@9.6.14...9.6.21)

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

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

Author: dependabot[bot]

poetry.lock

@@ -72,7 +72,7 @@ ruff = "0.13.3"
 
 [tool.poetry.group.docs.dependencies]
 mkdocs = { version = "1.6.1", python = ">=3.10" }
-mkdocs-material = { version = "9.6.14", python = ">=3.10" }
+mkdocs-material = { version = "9.6.21", python = ">=3.10" }
 mkdocstrings = { version = "0.30.1", extras = ["python"], python = ">=3.10" }
 
 [tool.poe.tasks]