[llvm] [LoopRotate] Remove canRotateDeoptimizingLatchExit and multi-rotate (PR #162482)

[Nikita Popov via llvm-commits]

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

If you're not making use of this downstream, then I agree that we should remove this code.

https://github.com/llvm/llvm-project/pull/162482