“Voyage,” ABBA A bouncy, synthy beat bridges the decades and brings ABBA into the present. “You look bewildered,” Agnetha Fältskog sings above the retro rhythm, “and you wonder why I’m here today.” Well, yes. While skeptics might ask why, the four Scandinavian septuagenarians decided why not, and “Voyage” does nothing to tarnish their legacy as global hitmakers. Ballads predominate on …