mypy

gh-133879: Copyedit "What's new in Python 3.15" (#144661) #19474

Job	Run time
Run mypy on Lib/_pyrepl	20s
Run mypy on Tools/jit	19s
Run mypy on Tools/build	18s
Run mypy on Tools/check-c-api-docs	15s
Run mypy on Lib/test/libregrtest	18s
Run mypy on Tools/cases_generator	20s
Run mypy on Lib/tomllib	15s
Run mypy on Tools/peg_generator	18s
Run mypy on Tools/clinic	21s
	2m 44s

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