[VPlan] Don't fold UDiv in replicate regions. (#175460)
The UDiv fold added in d12e993 (#174581) is currently also applied to
replicate regions, which means we may end up with VPInstructions in
replicate regions, which is currently nots supported.
Fixes https://github.com/llvm/llvm-project/issues/175295.
PR: https://github.com/llvm/llvm-project/pull/175460
