textproc/py-mkdocs-material: Update to 8.2.12

• Although there is already the release branch 8.5, first make a "minor" update to fix the real problem: To unbreak this port since the py-pygments update in 92ab9b1e2192.

Changelog:

https://github.com/squidfunk/mkdocs-material/compare/8.2.11...8.2.12

Reported by: otis, olgeni, pkg-fallout