mypy

gh-142518: add thread safety docs for set C-APIs (#146562) #20588

Job	Run time
Run mypy on Lib/_pyrepl	20s
Run mypy on Lib/test/libregrtest	22s
Run mypy on Tools/cases_generator	16s
Run mypy on Lib/tomllib	19s
Run mypy on Tools/clinic	19s
Run mypy on Tools/build	23s
Run mypy on Tools/jit	20s
Run mypy on Tools/check-c-api-docs	19s
Run mypy on Tools/peg_generator	15s
	2m 53s

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