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

[Sarah Spall via cfe-commits]

spall wrote:

> 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.

oh i thought this change did preserve that since this test should fail if such an error is produced? Or that was my thought. 

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