HONG KONG, July 8 (Reuters) - Ant Group on Saturday announced a share repurchase plan that values the fintech giant at 567.1 billion yuan ($78.54 billion), down from $315 billion when it tried to list in 2020, in a move that could allow some investors to exit after a lengthy regulatory overhaul of the firm. The news came one day after Ant was fined $984 million, which should end a years-long regulatory shake-up of the company and mark a key step to concluding a crackdown on the country's internet sector. Ant said it had proposed to all of its shareholders...