NEW YORK (Reuters) - As with most gossip, the full story of the New York Post writer investigated on suspicion he tried to extort a billionaire to keep his name out of the paper may never be known. Nine months after Jared Paul Stern, a contributor to New York's premiere gossip column Page Six in the Post, himself became tabloid fodder, federal prosecutors have dropped the case. Stern and his lawyer said on Wednesday they had been told by the U.S. Attorney's office that prosecutors will no longer pursue the investigation. That clears Stern legally, but he says his career...