DES MOINES — Republican gubernatorial hopeful Ron Corbett is confident he’ll be on the June 5 primary election ballot despite a complaint filed Wednesday that he failed to gather the minimum number of signatures required for his nomination petition.The former Cedar Rapids mayor, who also once served as Speaker of the Iowa House, said Wednesday he and his campaign staff spent much of last week reviewing the signatures and removing duplicates.Corbett has been gathering signatures for the past year as he competes with Gov.