chore(deps-dev): Bump mypy from 0.942 to 0.950

Bumps mypy from 0.942 to 0.950.

Commits

• cceba7b Update version to 0.950
• 48957aa Various documentation updates (mostly about error codes) (#12680)
• b84cda9 Fix types of inherited attributes in generic dataclasses (#12656)
• bf6b02d Attempt to fix issue with ParamSpec serialization (#12654)
• 1749cb7 Fix slots and deleted attributes in incremental mode (#12645)
• 2ff391c make_simplified_union: simpler and faster (#12630)
• 963e4ae more enum-related speedups (#12032)
• 914506b Fix type context for assert_type() (#12612)
• 851e89a Add support for assert_type (#12584)
• c4a9697 Sync typeshed (#12596)
• Additional commits viewable in compare view