mypy

bpo-39100: _header_value_parser: do not treat a Group as invalid-mail… #10493

Job	Run time
Run mypy on Lib/_pyrepl	23s
Run mypy on Tools/cases_generator	16s
Run mypy on Tools/peg_generator	19s
Run mypy on Lib/tomllib	20s
Run mypy on Lib/test/libregrtest	20s
Run mypy on Tools/check-c-api-docs	16s
Run mypy on Tools/clinic	20s
Run mypy on Tools/jit	16s
Run mypy on Tools/build	20s
	2m 50s

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