Sometime next month, the brick-clad Peabody/Englewood senior housing building at the crossroads of Peabody Square will be dressed up with a 1,500-square-foot mural created by a 30-year-old artist who grew up in Dorchester and Brighton. Mattaya Fitts, who moved to Brooklyn in December 2019 and works there for a professional mural company, will return in mid-May to paint a