[llvm] Revert "LangRef: Clarify llvm.minnum and llvm.maxnum about sNaN and signed zero (#112852)" (PR #138451)

[Phoebe Wang via llvm-commits]

phoebewang wrote:

@nikic @arsenm  Can we proceed the revert as the first step for now? It's near the holiday season and a new release window short after. I don't see a quick consensus can be made on what to do next, but let's not carry the controversial document into the next release at least.

https://github.com/llvm/llvm-project/pull/138451