gh-122229: Add missing `Py_DECREF` in `func_get_annotation_dict` (#12… #159

Job	Run time
Run mypy on Lib/_pyrepl	17s
Run mypy on Lib/test/libregrtest	19s
Run mypy on Tools/build	22s
Run mypy on Tools/cases_generator	18s
Run mypy on Tools/clinic	14s
Run mypy on Tools/jit	14s
Run mypy on Tools/peg_generator	31s
Run mypy on Tools/wasm	14s
	2m 29s

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