textproc/py-mkdocs: Update to 1.5.2

Changelogs since 1.4.3:

https://github.com/mkdocs/mkdocs/releases/tag/1.5.2
https://github.com/mkdocs/mkdocs/releases/tag/1.5.1
https://github.com/mkdocs/mkdocs/releases/tag/1.5.0

MFH: No (feature release)