Tests

Remove --force-union-syntax flag #19740

Job	Run time
Test mypyc suite with 32-bit Python	9m 3s
Test suite with py311-ubuntu	8m 43s
Test suite with py310-ubuntu, mypyc-compiled	13m 59s
Test suite with py313-ubuntu, mypyc-compiled	13m 58s
Parallel tests with py314-ubuntu, interpreted	23m 6s
mypyc runtime tests with py313-macos	5m 38s
Test suite with py312-ubuntu	9m 53s
Test suite with py314-windows-64	26m 34s
mypyc runtime tests with py310-ubuntu	4m 59s
Test suite with py314-ubuntu, mypyc-compiled	14m 1s
Parallel tests with py314-ubuntu, mypyc-compiled	26m 15s
Test suite with py314t-ubuntu, mypyc-compiled	15m 14s
Type check our own code (py310-ubuntu)	1m 40s
Type check our own code (py310-windows-64)	2m 58s
Formatting and code style with Black + ruff	1m 59s
	2h 58m 0s

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