[llvm] [UnifyFunctionExitNodes] skip mergereturn on terminating deoptimize/musttail (PR #204651)

[Nikita Popov via llvm-commits]

nikic wrote:

AMDGPUUnifyDivergentExitNodes uses continue for musttail.

Though as far as I can tell this is a dead pass that's not used by anything.

I think we can just go ahead and delete this pass.

https://github.com/llvm/llvm-project/pull/204651