mypy

gh-145921: Add "_DuringGC" functions for tp_traverse (GH-145925) #20506

Job	Run time
Run mypy on Lib/test/libregrtest	22s
Run mypy on Tools/cases_generator	20s
Run mypy on Tools/clinic	16s
Run mypy on Lib/_pyrepl	19s
Run mypy on Lib/tomllib	22s
Run mypy on Tools/build	19s
Run mypy on Tools/jit	22s
Run mypy on Tools/check-c-api-docs	20s
Run mypy on Tools/peg_generator	17s
	2m 57s

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