mypy

GH-144679: When building with VS 2026 on Windows, use PlatformToolset… #19589

Job	Run time
Run mypy on Tools/peg_generator	21s
Run mypy on Lib/tomllib	18s
Run mypy on Tools/jit	18s
Run mypy on Tools/check-c-api-docs	19s
Run mypy on Lib/_pyrepl	23s
Run mypy on Lib/test/libregrtest	19s
Run mypy on Tools/clinic	19s
Run mypy on Tools/build	19s
Run mypy on Tools/cases_generator	20s
	2m 56s

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