mypy

gh-151522: Guard against None transport in slow-socket SSL test (#151… #21918

Job	Run time
Run mypy on Lib/test/libregrtest	19s
Run mypy on Tools/build	13s
Run mypy on Lib/_pyrepl	18s
Run mypy on Lib/tomllib	16s
Run mypy on Tools/clinic	18s
Run mypy on Tools/cases_generator	17s
Run mypy on Tools/check-c-api-docs	21s
Run mypy on Tools/jit	22s
Run mypy on Tools/peg_generator	19s
	2m 43s

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