mypy

gh-149496: Fix MacOSTest.test_default regression when BROWSER env var… #21243

Job	Run time
Run mypy on Tools/clinic	29s
Run mypy on Lib/test/libregrtest	33s
Run mypy on Tools/check-c-api-docs	30s
Run mypy on Tools/jit	34s
Run mypy on Lib/_pyrepl	36s
Run mypy on Lib/tomllib	28s
Run mypy on Tools/build	29s
Run mypy on Tools/peg_generator	30s
Run mypy on Tools/cases_generator	25s
	4m 34s

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