[CUDA][HIP] Enable user_defined_reductions for cuda and hip. (#13057)

This patch enables user_defined_reductions.cpp for cuda and hip.
It's been verified that the test is now supported for cuda and hip now,
this closes #12613

Author: MaryaSharf

sycl/test-e2e/UserDefinedReductions/user_defined_reductions.cpp

@@ -1,7 +1,5 @@
 // RUN: %{build} -o %t.out
 // RUN: %{run} %t.out
-//
-// UNSUPPORTED: cuda || hip
 
 #include <complex>
 #include <numeric>