mypy

Default GHA permissions to `contents: read` #20605

Job	Run time
Run mypy on Tools/jit	16s
Run mypy on Tools/clinic	17s
Run mypy on Lib/_pyrepl	20s
Run mypy on Tools/cases_generator	16s
Run mypy on Tools/peg_generator	18s
Run mypy on Lib/test/libregrtest	18s
Run mypy on Tools/check-c-api-docs	15s
Run mypy on Tools/build	17s
Run mypy on Lib/tomllib	16s
	2m 33s

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