Remove shader variants from 16bit arithmetic sample #3360

Job	Run time
Build Ubuntu with Direct To Display	2m 24s
Build Android in Debug	13m 20s
Build windows in Debug	45m 14s
Build windows in Release	10m 39s
Build ios in Debug	27m 39s
Build ubuntu in Debug	4m 54s
Build ubuntu in Release	4m 29s
Build macos in Debug	4m 49s
Build macos in Release	4m 41s
	1h 58m 9s

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