NEW YORK — The media company Gannett, the nation’s largest newspaper chain and publisher of USA Today, said Tuesday it would stop using journalism from The Associated Press later this month, severing a century-old partnership.The decision “enables us to invest further in our newsrooms,” Gannett spokeswoman Lark-Marie Anton said. With more than 200 outlets, the chain represents more newspapers than any other company in AP’s U.S. membership. A memo from Gannett’s chief content officer…