Any protest or objection made pursuant to the Offstreet Parking District Act or any signature to such objection or protest may be withdrawn by a written withdrawal signed by the person or persons who signed the protest or objection or who affixed the signature to be withdrawn and filed with the city clerk at any time prior to the determination of the mayor and city council as to whether or not a protest exists. Any protest, objection, or signature withdrawn shall not be counted in computing the protest.