BUFFALO, N.Y. — The white supremacist who killed 10 Black people in a Buffalo supermarket was hustled out of a courtroom Wednesday after someone in the audience rushed at him and was restrained by a court officer.Payton Gendron’s sentencing in the attack, which was fueled by racist conspiracy theories he encountered online, resumed shortly after the disruption, which happened as Barbara Massey Mapps excoriated him for killing her 72-year-old sister, Katherine Massey. As Mapps shouted and pointed at Gendron, a …