mypy

gh-138122: New Tachyon UI (#142116) #18205

Job	Run time
Run mypy on Lib/test/libregrtest	15s
Run mypy on Lib/tomllib	18s
Run mypy on Tools/cases_generator	11s
Run mypy on Lib/_pyrepl	17s
Run mypy on Tools/build	17s
Run mypy on Tools/peg_generator	17s
Run mypy on Tools/jit	16s
Run mypy on Tools/clinic	17s
	2m 8s

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