mypy

gh-90483: fix docs of `SubprocessTransport.get_pipe_transport` (#137… #16187

Job	Run time
Run mypy on Lib/test/libregrtest	17s
Run mypy on Lib/_pyrepl	17s
Run mypy on Lib/tomllib	15s
Run mypy on Tools/peg_generator	11s
Run mypy on Tools/cases_generator	16s
Run mypy on Tools/jit	11s
Run mypy on Tools/clinic	15s
Run mypy on Tools/build	17s
	1m 59s

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