When a minor ward for whom a guardian has been appointed shall have attained his or her majority and has not been found incompetent and when any incompetent ward has been rated competent by the administration, a certificate of the administrator or his or her duly authorized representative to that effect shall be prima facie evidence that a guardian is no longer required and the court, upon the guardian filing a satisfactory final account, may discharge such guardian upon a petition filed for that purpose. Nothing contained in this section shall be construed to prevent a ward from filing a petition for the discharge of his or her guardian on the ground that the ward has attained majority or is competent or the court from acting on its own motion in such cases.