mypy

gh-137928: remove redundant size validation in multiprocessing.heap (… #17872

Job	Run time
Run mypy on Lib/tomllib	19s
Run mypy on Tools/jit	20s
Run mypy on Tools/cases_generator	17s
Run mypy on Tools/clinic	17s
Run mypy on Tools/build	18s
Run mypy on Lib/_pyrepl	22s
Run mypy on Tools/peg_generator	18s
Run mypy on Lib/test/libregrtest	19s
	2m 30s

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