message: fix device_matrix_data GPU tests
diff: @@ -350,7 +350,7 @@ TYPED_TEST(DeviceMatrixData, SumsDuplicates)
  auto device_data =
  device_matrix_data::create_from_host(this->exec, this->duplicate_data);
  auto ref_device_data = device_matrix_data::create_from_host(
  - this->exec, this->deduplicated_data);
  + this->exec->get_master(), this->deduplicated_data);
  device_data.sum_duplicates();
  @@ -359,6 +359,7 @@ TYPED_TEST(DeviceMatrixData, SumsDuplicates)
  GKO_ASSERT_ARRAY_EQ(arrays.row_idxs, ref_arrays.row_idxs);
  GKO_ASSERT_ARRAY_EQ(arrays.col_idxs, ref_arrays.col_idxs);
  double max_error{};
  + arrays.values.set_executor(this->exec->get_master());
  for (int i = 0; i < arrays.values.get_num_elems(); i++) {
  max_error = std::max<double>(
  max_error, std::abs(arrays.values.get_const_data()[i] -
  