[llvm] [Offload] Remove unnecessary omp CMake target dependencies (PR #149060)

[Shilei Tian via llvm-commits]

shiltian wrote:

> > IIRC there are indeed some function calls from `libomptarget` to `libomp`.
> 
> Yeah, there are a few but I forget which ones. Did this really build and pass the tests?

Those `nowait` handling related stuff also depends on `libomp`.

https://github.com/llvm/llvm-project/pull/149060