mypy

gh-75723: Fix double evaluation of .pth and .site files in venvs (#14… #21263

Job	Run time
Run mypy on Tools/jit	46s
Run mypy on Lib/test/libregrtest	41s
Run mypy on Tools/cases_generator	44s
Run mypy on Lib/tomllib	38s
Run mypy on Lib/_pyrepl	47s
Run mypy on Tools/clinic	41s
Run mypy on Tools/build	47s
Run mypy on Tools/check-c-api-docs	39s
Run mypy on Tools/peg_generator	45s
	6m 28s

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