B y Julie Zhu HONG KONG, June 9 (Reuters) - China's central leadership has given billionaire Jack Ma's Ant Group a tentative green light to revive its initial public offering (IPO), two sources with knowledge of the matter said, in the clearest sign yet Beijing is easing its crackdown on the tech sector. Ant, an affiliate of Chinese e-commerce behemoth Alibaba Group Holding Ltd 9988.HK , aims to file a preliminary prospectus for the share offering in Shanghai and Hong Kong as early as next month, the sources said, declining to be named due to the sensitivity of the matter....