mypy

GH-143732: SEND specialization #21158

Job	Run time
Run mypy on Tools/cases_generator	12s
Run mypy on Tools/peg_generator	20s
Run mypy on Tools/check-c-api-docs	20s
Run mypy on Tools/build	14s
Run mypy on Tools/clinic	18s
Run mypy on Lib/test/libregrtest	14s
Run mypy on Tools/jit	21s
Run mypy on Lib/_pyrepl	22s
Run mypy on Lib/tomllib	18s
	2m 39s

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