Nobody ever wants to pay taxes. The sentiment is in the air — April 18 is Tax Day! — as well as the arts. “Funmilayo,” the fourth production in the African opera series at Mount Holyoke, explores just one moment in the rich life of Funmilayo Ransome-Kuti: when she fought British colonial rule in what is now present-day Nigeria through protests against a special tax imposed on women in the 1940s.