mypy

gh-151126: Fix missing memory errors in `_interpchannelsmodule.c` (#1… #21822

Job	Run time
Run mypy on Lib/test/libregrtest	22s
Run mypy on Tools/jit	18s
Run mypy on Lib/tomllib	23s
Run mypy on Tools/cases_generator	21s
Run mypy on Tools/peg_generator	23s
Run mypy on Tools/build	17s
Run mypy on Tools/clinic	22s
Run mypy on Lib/_pyrepl	19s
Run mypy on Tools/check-c-api-docs	16s
	3m 1s

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