build(deps-dev): Bump mkdocstrings from 0.20.0 to 0.21.1
Bumps [mkdocstrings](https://github.com/mkdocstrings/mkdocstrings) from 0.20.0 to 0.21.1.
- [Release notes](https://github.com/mkdocstrings/mkdocstrings/releases)
- [Changelog](https://github.com/mkdocstrings/mkdocstrings/blob/master/CHANGELOG.md)
- [Commits](https://github.com/mkdocstrings/mkdocstrings/compare/0.20.0...0.21.1)
---
updated-dependencies:
- dependency-name: mkdocstrings
dependency-type: direct:development
update-type: version-update:semver-minor
...
Signed-off-by: dependabot[bot] <support@github.com>