mypy

gh-144156: Fix email header folding concatenating encoded words (#144… #2

Job	Run time
Run mypy on Tools/build	23s
Run mypy on Tools/jit	18s
Run mypy on Tools/cases_generator	21s
Run mypy on Tools/peg_generator	18s
Run mypy on Tools/check-c-api-docs	18s
Run mypy on Lib/_pyrepl	21s
Run mypy on Lib/test/libregrtest	20s
Run mypy on Lib/tomllib	18s
Run mypy on Tools/clinic	21s
	2m 58s

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