[llvm] [NVPTX] disable combine-mad test for newer ptxas (PR #93919)

[Artem Belevich via llvm-commits]

https://github.com/Artem-B approved this pull request.

The change should apply to line 4 only. The change itself is fine.

You can (and should run LLVM tests with `LLVM_PTXAS_EXECUTABLE=` set to point to `ptxas` from a recent CUDA version.

https://github.com/llvm/llvm-project/pull/93919