WASHINGTON — The U.S. Supreme Court turned away a challenge today to Google’s online book library from authors who complained that the project makes it harder for them to market their work.The justices let stand lower court rulings in favor of Mountain View, Calif.-based Google and rejected the authors’ claim that the company’s digitizing of millions of books amounts to “copyright infringement on an epic scale.”Lower courts have said that Google can provide small portions of the books to …