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

[Ralf Jung via llvm-commits]

RalfJung wrote:

This got reverted in https://github.com/llvm/llvm-project/pull/170067, re-introducing all the problems with https://github.com/llvm/llvm-project/pull/112852.

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