Oct. 22—Two days after he became an unlikely hero without ever taking a swing, the biggest at-bat of Jon Singleton’s life was superseded by another. With two outs and the bases loaded in the bottom of the eighth inning, needing two runs to tie the game and one win to advance to the World Series, the Astros summoned Singleton to pinch-hit for shortstop Jeremy Peña. The venue was Minute Maid Park…