The most significant figure in the history of Nevada Wolf Pack sports is no longer associated with the university.Head football coach Chris Ault, who spent four decades as a Wolf Pack athlete, coach and administrator, announced his retirement Friday afternoon at Legacy Hall."Change is inevitable," Ault said, fighting back his emotions in the Hall of Fame room of Legacy Hall, the building he helped build as athletic director from 1986-2004. "It is with great humility and mixed emotions that I've decided it's time for me to step down and move on."Ault, who said he didn't tell anyone of his decision …