mypy

gh-138199: Address potential confusion regarding threading in the `as… #18112

Job	Run time
Run mypy on Lib/tomllib	18s
Run mypy on Lib/test/libregrtest	22s
Run mypy on Lib/_pyrepl	19s
Run mypy on Tools/jit	23s
Run mypy on Tools/clinic	16s
Run mypy on Tools/peg_generator	23s
Run mypy on Tools/build	30s
Run mypy on Tools/cases_generator	20s
	2m 51s

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