Updates the requirements on [mkdocstrings](https://github.com/mkdocstrings/mkdocstrings) to permit the latest version.
- [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/0.21.1...0.21.2)
---
updated-dependencies:
- dependency-name: mkdocstrings
dependency-type: direct:development
...
Signed-off-by: dependabot[bot] <support@github.com>