[SYCL][HIP] Re-enable reduction nd lambda test (intel#12395)

This test is now passing.

It is noted as inconsistently failing, I couldn't reproduce the failure
locally and the CI passed, so I'd like to try to re-enable it as we
improved the HIP backend significantly since it was disabled.

I will keep an eye out and revert this if it starts failing again.

Author: npmiller

sycl/test-e2e/Reduction/reduction_nd_lambda.cpp

@@ -1,9 +1,6 @@
 // RUN: %{build} -o %t.out
 // RUN: %{run} %t.out
 //
-// Inconsistently fails on HIP AMD, HIP Nvidia.
-// UNSUPPORTED: hip_amd || hip_nvidia
-
 // Windows doesn't yet have full shutdown().
 // UNSUPPORTED: ze_debug && windows