mypy

gh-146228: Better fork support in cached FastPath (#146231) #20076

Job	Run time
Run mypy on Lib/test/libregrtest	17s
Run mypy on Tools/cases_generator	19s
Run mypy on Tools/clinic	15s
Run mypy on Lib/tomllib	17s
Run mypy on Tools/build	17s
Run mypy on Tools/check-c-api-docs	20s
Run mypy on Tools/jit	16s
Run mypy on Tools/peg_generator	17s
Run mypy on Lib/_pyrepl	20s
	2m 38s

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