[llvm] [AMDGPU] Remove unnecessary predicates from aliases. NFC. (PR #91602)

[Joe Nash via llvm-commits]

Sisyph wrote:

I think that since Requires is the last defined class in def _gfx12 ..., only the predicates in Requires will apply to the whole instruction definition. So is it Ok to remove HasExportInsts from this instruction? It might be if isGFX12Plus implies HasExportInsts

https://github.com/llvm/llvm-project/pull/91602