Tests

Revert dict.or typeshed change #21597

Job	Run time
Test mypyc suite with 32-bit Python	9m 37s
Test suite with py310-ubuntu, mypyc-compiled	16m 6s
mypyc runtime tests with py313-macos	7m 12s
Test suite with py311-ubuntu	9m 6s
Test suite with py314-ubuntu, mypyc-compiled	15m 14s
Test suite with py313-ubuntu, mypyc-compiled	15m 23s
Type check our own code (py310-windows-64)	2m 48s
mypyc runtime tests with py310-ubuntu	6m 32s
Test suite with py312-ubuntu	9m 34s
Test suite with py314-windows-64	25m 43s
Parallel tests with py314-ubuntu, mypyc-compiled	26m 3s
Type check our own code (py310-ubuntu)	1m 45s
Parallel tests with py314-windows-64, interpreted	10m 27s
Test suite with py314t-ubuntu, mypyc-compiled	19m 27s
Parallel tests with py314-ubuntu, interpreted	23m 26s
Formatting and code style with Black + ruff	1m 51s
	3h 20m 14s

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