[clang] [AMDGPU] Remove detection of hip runtime for Spack (PR #133263)

[Yaxun Liu via cfe-commits]

yxsamliu wrote:

> I'm going to wager that we can't just rip this out without the world exploding, and these issues need to be addressed and not just drop the whole thing.

[haampie](https://github.com/haampie) is the maintainer of the HIP spack package. I assume it is safe to remove them by his request.

https://github.com/llvm/llvm-project/pull/133263