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

[Ralf Jung via llvm-commits]

https://github.com/RalfJung approved this pull request.

This makes sense to me -- at least from a Rust perspective, this is the spec we expect and desire. It seems like https://github.com/llvm/llvm-project/pull/112852 changed the contract for these intrinsics without actually updating all backends to match the new contract, and some backends really don't like the new contract, so we should revert to something more backend-friendly.

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