[openmp] [llvm] [clang] [OpenMP] Remove `register_requires` global constructor (PR #80460)

[Sergio Afonso via cfe-commits]

https://github.com/skatrak commented:

I noticed a small breakage of the OpenMP MLIR dialect from one of these changes. It should be trivial to address.

https://github.com/llvm/llvm-project/pull/80460