mypy

gh-150436: Check returncode in Win32ProcessTestCase (#150972) #21744

Job	Run time
Run mypy on Lib/tomllib	21s
Run mypy on Lib/test/libregrtest	20s
Run mypy on Tools/build	17s
Run mypy on Tools/clinic	20s
Run mypy on Tools/peg_generator	19s
Run mypy on Tools/cases_generator	20s
Run mypy on Lib/_pyrepl	19s
Run mypy on Tools/jit	22s
Run mypy on Tools/check-c-api-docs	22s
	3m 0s

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