By Pat Forde The backstroke world-record holder is leaving Stanford and moving her training base to Arizona State to join a pro group. Tokyo Olympic medalist and backstroke world-record holder Regan Smith is turning professional, leaving Stanford and moving her training base to Arizona State, the swimmer announced Tuesday. The 20-year-old Smith will join the burgeoning pro group of Sun Devils coach Bob Bowman, who coached Michael Phelps throughout his unparalleled career. Smith, who set the world record in the 200-meter backstroke at FINA World Championships in 2019, also previously held the w…