Tests

Remove --force-union-syntax flag #19739

Job	Run time
Test mypyc suite with 32-bit Python	9m 8s
Test suite with py314t-ubuntu, mypyc-compiled	16m 39s
Test suite with py314-ubuntu, mypyc-compiled	14m 50s
Parallel tests with py314-ubuntu, interpreted	25m 0s
Test suite with py313-ubuntu, mypyc-compiled	13m 51s
mypyc runtime tests with py313-macos	4m 46s
Type check our own code (py310-windows-64)	2m 25s
Type check our own code (py310-ubuntu)	1m 40s
Test suite with py311-ubuntu	8m 43s
Test suite with py314-windows-64	27m 44s
Test suite with py312-ubuntu	10m 1s
mypyc runtime tests with py310-ubuntu	5m 4s
Parallel tests with py314-ubuntu, mypyc-compiled	27m 30s
Formatting and code style with Black + ruff	1m 55s
Test suite with py310-ubuntu, mypyc-compiled	13m 56s
	3h 3m 12s

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