RIO DE JANEIRO — Undefeated, uncatchable, unquestionably the best. Usain Bolt bid a blazing-fast farewell to the Rio de Janeiro Games — and likely the Olympics altogether — Friday night with yet another anchor leg for the ages. He turned a close 4×100 relay race against Japan and the United States into a never-a-doubt runaway, helping Jamaica cross the line in 37.27. “There you go,” he said.