[llvm] [OpenMP] Remove 'omp assumes' scopes now that we have no inline ASM (PR #123611)

[Michael Kruse via llvm-commits]

================
@@ -100,6 +100,7 @@ set(bc_flags -c -foffload-lto -std=c++17 -fvisibility=hidden
              -nocudalib -nogpulib -nogpuinc -nostdlibinc
              -fopenmp -fopenmp-cuda-mode
              -Wno-unknown-cuda-version -Wno-openmp-target
+             -Wno-unknown-assumption
----------------
Meinersbur wrote:

```suggestion
             -Wno-unknown-assumption  # TODO: Fix false-positive warning for ext_aligned_barrier
```
For anyone encountering this to understand why it is there

https://github.com/llvm/llvm-project/pull/123611