mypy

Docs: fix a form error and a grammatical error in float.rst (#140989) #19971

Job	Run time
Run mypy on Tools/cases_generator	19s
Run mypy on Lib/tomllib	17s
Run mypy on Tools/peg_generator	20s
Run mypy on Lib/_pyrepl	19s
Run mypy on Tools/jit	21s
Run mypy on Tools/build	19s
Run mypy on Tools/check-c-api-docs	18s
Run mypy on Tools/clinic	18s
Run mypy on Lib/test/libregrtest	21s
	2m 52s

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