Remove some unused functions. #13739

Job	Run time
Test mypyc suite with 32-bit Python	7m 12s
Test suite with py38-ubuntu, mypyc-compiled	18m 41s
Test suite with py38-windows-64	19m 44s
Test suite with py39-ubuntu	16m 40s
Test suite with py310-ubuntu	16m 1s
Test suite with py311-ubuntu, mypyc-compiled	15m 59s
Test suite with py312-ubuntu, mypyc-compiled	17m 30s
Test suite with py313-ubuntu, mypyc-compiled	18m 20s
mypyc runtime tests with py39-macos	6m 2s
Type check our own code (py38-ubuntu)	1m 57s
Type check our own code (py38-windows-64)	2m 22s
Formatting and code style with Black + ruff	37s
	2h 21m 5s

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