[llvm] [NFC][OpenMP] Update a test that was failing on aarch64. (PR #164456)

[Abhinav Gaba via llvm-commits]

abhinavgaba wrote:


>
```
.../offload/test/aarch64-unknown-linux-gnu/offloading/Output/bug51781.c.tmp.custom'
# | /usr/bin/aarch64-unknown-linux-gnu-ld: unrecognised emulation mode: llvm=-openmp-opt-disable-spmdization
...
```
The flag has been used in that test for a long time (51168ce8d574360a50446c5795b9f5a68c693fca). I'm not sure if something broke it recently.



https://github.com/llvm/llvm-project/pull/164456