BOSTON — For the first time in 200 years, Boston voters have narrowed the field of mayoral candidates to two women of color who will face off against each other in November.City Councilors Michelle Wu and Annissa Essaibi George topped the five-person race in Tuesday’s preliminary runoff. They bested acting Mayor Kim Janey, City Councilor Andrea Campbell and John Barros, the city’s former economic development chief. All five were candidates of color — a major shift away from two centuries of Boston politics dominated by …