AtomicCompareExchangeWeak is deprecated after v1.3

[iliya-diyachkov]

The commit a4161be "[SPIR-V] Add missing OpAtomicCompareExchangeWeak instruction" caused the SPIRV verifier degradation on one LIT test transcoding/AtomicCompareExchangeExplicit_cl20.ll because OpAtomicCompareExchangeWeak is missing after version 1.3.