MIAMI — At the request of the Cuban government, American Airlines did not allow Cuban activist Anamely Ramos to board a flight at Miami International Airport bound for Havana on Wednesday. Ramos, an art professor and member of the opposition group San Isidro Movement, was trying to return to Havana from Miami, where she was visiting, when airline employees prevented her from boarding, telling her that the island’s authorities were denying her entry into the country. The Cuban government has frequently denied entry to opponents and activists, but usually after they’ve already arrived on the isl…