[llvm] Revert "LangRef: Clarify llvm.minnum and llvm.maxnum about sNaN and signed zero (#112852)" (PR #168838)

[Ralf Jung via llvm-commits]

RalfJung wrote:

FWIW I have no approval rights in LLVM, so my review doesn't really count for much I think. :)

https://github.com/llvm/llvm-project/pull/168838