mypy

gh-143309: fix UAF in `os.execve` when the environment is concurrentl… #10024

Job	Run time
Run mypy on Tools/build	17s
Run mypy on Tools/check-c-api-docs	16s
Run mypy on Tools/jit	17s
Run mypy on Lib/test/libregrtest	21s
Run mypy on Tools/cases_generator	16s
Run mypy on Tools/clinic	17s
Run mypy on Tools/peg_generator	18s
Run mypy on Lib/_pyrepl	17s
Run mypy on Lib/tomllib	17s
	2m 36s

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