mypy

gh-149879: Fix test_ftplib on Cygwin (#150431) #21564

Job	Run time
Run mypy on Tools/check-c-api-docs	17s
Run mypy on Tools/cases_generator	20s
Run mypy on Lib/_pyrepl	21s
Run mypy on Tools/build	19s
Run mypy on Tools/jit	19s
Run mypy on Lib/test/libregrtest	21s
Run mypy on Lib/tomllib	18s
Run mypy on Tools/clinic	19s
Run mypy on Tools/peg_generator	19s
	2m 53s

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