chore(deps-dev): bump mkdocs-material from 9.6.19 to 9.6.21

Bumps [mkdocs-material](https://github.com/squidfunk/mkdocs-material) from 9.6.19 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@9.6.19...9.6.21)

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

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

poetry.lock

@@ -52,7 +52,7 @@ docstr-coverage = "^2.3"
 cffconvert = "^2.0"
 cryptography = {version = "^46.0.2", markers = "python_version != '3.9.0' and python_version != '3.9.1'"}
 mkdocs = "^1.6.1"
-mkdocs-material = "^9.6.18"
+mkdocs-material = "^9.6.21"
 mkdocstrings = {extras = ["python"], version = "^0.30.0"}
 mkdocs-jupyter = "^0.25.1"
 bandit = "^1.8.6"