message: improve sorting test output
diff: @@ -125,8 +125,7 @@ TEST_F(Sorting, CudaBitonicSortWarp)
  auto data_ptr = ddata.get_const_data();
  auto ref_ptr = ref_warp.get_const_data();
  - ASSERT_TRUE(std::equal(data_ptr, data_ptr + (num_local * config::warp_size),
  - ref_ptr));
  + GKO_ASSERT_ARRAY_EQ(ddata, ref_warp);
  }
  @@ -137,7 +136,7 @@ TEST_F(Sorting, CudaBitonicSortShared)
  auto data_ptr = ddata.get_const_data();
  auto ref_ptr = ref_shared.get_const_data();
  - ASSERT_TRUE(std::equal(data_ptr, data_ptr + num_elements, ref_ptr));
  + GKO_ASSERT_ARRAY_EQ(ddata, ref_shared);
  }
  