mypy

gh-138122: Default highlight to sh (#143782) #10076

Job	Run time
Run mypy on Lib/tomllib	18s
Run mypy on Tools/cases_generator	18s
Run mypy on Tools/clinic	17s
Run mypy on Tools/build	17s
Run mypy on Tools/check-c-api-docs	17s
Run mypy on Lib/_pyrepl	18s
Run mypy on Lib/test/libregrtest	19s
Run mypy on Tools/jit	19s
Run mypy on Tools/peg_generator	16s
	2m 39s

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