[llvm] [RemoveDIs] Use iterators for moving PHIs in loop-unroll-and-jam (PR #83003)

[Orlando Cazalet-Hyams via llvm-commits]

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

I think not-adding a test fits with the existing strategy for these kinds of fixes - LGTM 

https://github.com/llvm/llvm-project/pull/83003