mypy

gh-90483: fix docs of `SubprocessTransport.get_pipe_transport` (#137… #9491

Job	Run time
Run mypy on Lib/test/libregrtest	15s
Run mypy on Lib/_pyrepl	18s
Run mypy on Tools/build	16s
Run mypy on Tools/peg_generator	19s
Run mypy on Tools/cases_generator	17s
Run mypy on Lib/tomllib	12s
Run mypy on Tools/clinic	15s
Run mypy on Tools/jit	16s
	2m 8s

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