mypy

gh-141650: Fix typo in `xml.sax.saxutils.unescape` documentation (#14… #18000

Job	Run time
Run mypy on Lib/test/libregrtest	18s
Run mypy on Lib/_pyrepl	20s
Run mypy on Tools/cases_generator	18s
Run mypy on Tools/build	19s
Run mypy on Tools/jit	16s
Run mypy on Tools/peg_generator	21s
Run mypy on Tools/clinic	17s
Run mypy on Lib/tomllib	16s
	2m 25s

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