mypy

gh-134584: Eliminate redundant refcounting from `_LOAD_ATTR_INSTANCE_… #18578

Job	Run time
Run mypy on Tools/cases_generator	16s
Run mypy on Lib/_pyrepl	19s
Run mypy on Tools/clinic	19s
Run mypy on Tools/jit	21s
Run mypy on Tools/peg_generator	20s
Run mypy on Tools/build	21s
Run mypy on Lib/test/libregrtest	18s
Run mypy on Lib/tomllib	17s
	2m 31s

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