mypy

Mark PRs as stale after 90 days (#150104) #21427

Job	Run time
Run mypy on Tools/cases_generator	19s
Run mypy on Lib/_pyrepl	21s
Run mypy on Lib/test/libregrtest	17s
Run mypy on Tools/peg_generator	20s
Run mypy on Lib/tomllib	16s
Run mypy on Tools/check-c-api-docs	18s
Run mypy on Tools/build	17s
Run mypy on Tools/jit	21s
Run mypy on Tools/clinic	20s
	2m 49s

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