Stubtest: ignore `_ios_support` (#17270) #12424

Job	Run time
Test suite with py38-ubuntu, mypyc-compiled	17m 9s
Test suite with py38-windows-64	19m 36s
Test suite with py39-ubuntu	16m 29s
Test suite with py310-ubuntu	15m 29s
Test suite with py311-ubuntu, mypyc-compiled	15m 47s
Test suite with py312-ubuntu, mypyc-compiled	17m 55s
mypyc runtime tests with py39-macos	5m 52s
mypyc runtime tests with py38-debug-build-ubuntu	4m 41s
Type check our own code (py38-ubuntu)	1m 51s
Type check our own code (py38-windows-64)	2m 35s
Formatting and code style with Black + ruff	38s
Test mypyc suite with 32-bit Python	7m 30s
	2h 5m 32s

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