[llvm] remove references to hard-coded gc strategies (PR #94401)

[Dwight Guth via llvm-commits]

dwightguth wrote:

@preames I believe in the past I have spoken to you about our efforts to make use of llvm's statepoints, and I see you in the history of these files. I don't have the ability to request reviewers, but I thought you might want to take a look.

https://github.com/llvm/llvm-project/pull/94401