message: Changed the executor from the cpu cg solver from Default to CpuExecutor
diff: @@ -54,7 +54,7 @@ void initialize(std::shared_ptr<const CpuExecutor> exec,
  GKO_INSTANTIATE_FOR_EACH_VALUE_TYPE(GKO_DECLARE_CG_INITIALIZE_KERNEL);
  template <typename ValueType>
  -void test_convergence(std::shared_ptr<const DefaultExecutor> exec,
  +void test_convergence(std::shared_ptr<const CpuExecutor> exec,
  const matrix::Dense<ValueType> *tau,
  const matrix::Dense<ValueType> *orig_tau,
  remove_complex<ValueType> rel_residual_goal,
  