Tests

Remove special case for Union type context #20212

Job	Run time
Test mypyc suite with 32-bit Python	9m 38s
Test suite with py313-ubuntu, mypyc-compiled	14m 33s
Test suite with py314t-ubuntu, mypyc-compiled	17m 31s
Type check our own code (py310-ubuntu)	1m 29s
Test suite with py310-ubuntu, mypyc-compiled	15m 29s
Test suite with py312-ubuntu	9m 44s
mypyc runtime tests with py310-ubuntu	5m 39s
Test suite with py311-ubuntu	9m 31s
Parallel tests with py314-ubuntu, mypyc-compiled	27m 57s
mypyc runtime tests with py313-macos	4m 43s
Parallel tests with py314-ubuntu, interpreted	24m 10s
Test suite with py314-ubuntu, mypyc-compiled	15m 2s
Formatting and code style with Black + ruff	1m 57s
Type check our own code (py310-windows-64)	2m 43s
Test suite with py314-windows-64	27m 26s
	3h 7m 32s

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