[clang] [HLSL] Simplify test (PR #165743)

[Justin Bogner via cfe-commits]

https://github.com/bogner approved this pull request.

This looks reasonable and correct, but the test may also deserve a `CHECK-NOT: "-S"` to preserve the regression test that #97001 attempted to add here. Admittedly though, that kind of test can be a bit fragile and this particular issue is somewhat unlikely to regress, so I could be convinced we don't really need it.

https://github.com/llvm/llvm-project/pull/165743