mypy

gh-143939: Fix assignment to `_PyThreadStateImpl.generator_return_kin… #19187

Job	Run time
Run mypy on Lib/tomllib	19s
Run mypy on Tools/check-c-api-docs	17s
Run mypy on Lib/_pyrepl	17s
Run mypy on Tools/peg_generator	18s
Run mypy on Tools/clinic	16s
Run mypy on Tools/build	19s
Run mypy on Tools/jit	17s
Run mypy on Tools/cases_generator	20s
Run mypy on Lib/test/libregrtest	22s
	2m 45s

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