mypy

gh-150866: Fix asyncio shutdown_asyncgens to report BaseException (#1… #22813

Job	Run time
Run mypy on Tools/peg_generator	19s
Run mypy on Tools/check-c-api-docs	17s
Run mypy on Lib/test/libregrtest	16s
Run mypy on Tools/jit	19s
Run mypy on Tools/cases_generator	18s
Run mypy on Tools/clinic	23s
Run mypy on Lib/tomllib	17s
Run mypy on Tools/build	18s
Run mypy on Lib/_pyrepl	15s
	2m 42s

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