mypy

GH-134584: Remove redundant refcount for `BINARY_OP_SUBSCR_STR_INT` (… #18667

Job	Run time
Run mypy on Tools/build	20s
Run mypy on Lib/_pyrepl	20s
Run mypy on Tools/check-c-api-docs	18s
Run mypy on Tools/cases_generator	19s
Run mypy on Lib/test/libregrtest	18s
Run mypy on Tools/peg_generator	16s
Run mypy on Lib/tomllib	19s
Run mypy on Tools/jit	16s
Run mypy on Tools/clinic	18s
	2m 44s

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