Anna Deavere Smith, a champion of the everyman, Black rights, and justice, is one of the most prolific playwrights of our time. A force to be reckoned with, she has revised her stunning play, “Twilight: Los Angeles, 1992,” from a one-woman play that she performed in the past, to its current incarnation as a five-actor play, being shown at the Signature Theatre and incorporating the murder of George Floyd into the scenario.