mypy

gh-151179: Fix pidfd leak in asyncio _PidfdChildWatcher (#151186) #21844

Job	Run time
Run mypy on Lib/_pyrepl	22s
Run mypy on Tools/check-c-api-docs	19s
Run mypy on Tools/jit	18s
Run mypy on Lib/tomllib	16s
Run mypy on Lib/test/libregrtest	21s
Run mypy on Tools/build	17s
Run mypy on Tools/cases_generator	21s
Run mypy on Tools/peg_generator	22s
Run mypy on Tools/clinic	19s
	2m 55s

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