mypy

gh-143445: Optimize deepcopy for 1.04x speedup (#143449) #10041

Job	Run time
Run mypy on Lib/tomllib	20s
Run mypy on Tools/cases_generator	23s
Run mypy on Tools/jit	17s
Run mypy on Tools/build	16s
Run mypy on Tools/peg_generator	20s
Run mypy on Tools/clinic	21s
Run mypy on Lib/_pyrepl	19s
Run mypy on Tools/check-c-api-docs	17s
Run mypy on Lib/test/libregrtest	21s
	2m 54s

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