mypy

gh-148688: Fix _BlocksOutputBuffer_Finish() double free (#148689) #10442

Job	Run time
Run mypy on Tools/build	17s
Run mypy on Tools/check-c-api-docs	17s
Run mypy on Lib/_pyrepl	20s
Run mypy on Tools/clinic	18s
Run mypy on Tools/jit	17s
Run mypy on Lib/test/libregrtest	17s
Run mypy on Tools/peg_generator	20s
Run mypy on Tools/cases_generator	15s
Run mypy on Lib/tomllib	17s
	2m 38s

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