stubtest: changes for py313 #12403

Job	Run time
Test mypyc suite with 32-bit Python	7m 12s
Test suite with py38-ubuntu, mypyc-compiled	17m 15s
Test suite with py38-windows-64	19m 44s
Test suite with py39-ubuntu	16m 1s
Test suite with py310-ubuntu	16m 36s
Test suite with py311-ubuntu, mypyc-compiled	15m 15s
Test suite with py312-ubuntu, mypyc-compiled	17m 27s
mypyc runtime tests with py39-macos	5m 27s
mypyc runtime tests with py38-debug-build-ubuntu	4m 32s
Type check our own code (py38-ubuntu)	1m 51s
Type check our own code (py38-windows-64)	2m 38s
Formatting and code style with Black + ruff	35s
	2h 4m 33s

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