[llvm] [SPIR-V] Allow NoUnsignedWrap decoration on OpShiftLeftLogical (PR #206155)

[Arseniy Obolenskiy via llvm-commits]

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aobolensk wrote:

> Should we remove OpSNegate from here then?

I'd conservatively leave it as is. Anyway it does not break anything

> Should we merge these 2 helpers since they converged?

That's right, this is a good solution. Done

https://github.com/llvm/llvm-project/pull/206155