By LORETTA FULTON Seventy-one years after preaching his first sermon, Jack Ridlehoover is stepping down–but not from everything. He’s just giving up his regular meetings with fellow pastors at the Abilene-Callahan Baptist Association office. For now, at least, he will continue his Minister’s Mentoring and Consulting Service. At his final session on May 6, Ridlehoover, 88, offered some words of