Rubble, rubble everywhere, and not a gumdrop in sight. With a last curtsy, Salt Lake's 51-year-old downtown landmark theater, the Centre, has gone the way of the double feature. And since it's April and tax month, the action might lead to an expanded version of that old list of dependable misfortunes: Add a wrecking ball to death and taxes. But movie addicts should hold tight. The new $24 million, 14-story office complex promised for the the corner of State Street and Third South by March 1991 will include four movie screens. Actually, this is the second start of demolition on the art deco theater. City building inspectors stopped the work on the 45-day project last week when it was begun without protective barriers in place.