mypy

gh-145998: Remove duplicated "What's New in 3.15" entry (#145994) #19966

Job	Run time
Run mypy on Lib/tomllib	16s
Run mypy on Lib/test/libregrtest	18s
Run mypy on Lib/_pyrepl	18s
Run mypy on Tools/cases_generator	16s
Run mypy on Tools/check-c-api-docs	17s
Run mypy on Tools/build	17s
Run mypy on Tools/peg_generator	18s
Run mypy on Tools/jit	18s
Run mypy on Tools/clinic	17s
	2m 35s

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