[llvm] [NFC][SelectionDAG] Replace generic @llvm.expect.with.probability codegen test with X86 test (PR #117848)

[via llvm-commits]

antangelo wrote:

> Any reason not to keep the generic test as well to help sniff out regression on other targets?

I was told to remove it in the GISel patch to fix the same issue: https://github.com/llvm/llvm-project/pull/117835#discussion_r1859753618

This is my first set of patches to the generic backend code, so I'm not sure what the best testing methodology is or degree to which tests should be generic vs specific to various backends.

https://github.com/llvm/llvm-project/pull/117848