mypy

gh-133879: Copyedit "What's new in Python 3.15" (#145737) #19855

Job	Run time
Run mypy on Tools/check-c-api-docs	21s
Run mypy on Tools/build	16s
Run mypy on Lib/tomllib	19s
Run mypy on Lib/test/libregrtest	19s
Run mypy on Tools/cases_generator	30s
Run mypy on Lib/_pyrepl	19s
Run mypy on Tools/clinic	19s
Run mypy on Tools/jit	21s
Run mypy on Tools/peg_generator	18s
	3m 2s

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