mypy

gh-128563: Move assignment of opcode into ifdef #12182

Job	Run time
Run mypy on Lib/_pyrepl	14s
Run mypy on Lib/test/libregrtest	21s
Run mypy on Tools/build	16s
Run mypy on Tools/cases_generator	14s
Run mypy on Tools/clinic	14s
Run mypy on Tools/jit	17s
Run mypy on Tools/peg_generator	21s
Run mypy on Tools/wasm	20s
	2m 17s

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