[flang] [llvm] [Frontend][OpenMP] Reduction modifier must be applied somewhere (PR #92160)

[Pete Steinfeld via llvm-commits]

psteinfeld wrote:

@kparzysz, I'm still getting an assertion in Decomposer.cpp with my internal test even with this latest change.  Are you still working on this, or should I work to create a small reproducer?

https://github.com/llvm/llvm-project/pull/92160