(Reuters) – Twitter Inc’s shares retreated further from Elon Musk’s offer price on Thursday as investors fretted over financing for the proposed $44-billion buyout of the social media firm against the backdrop of growing economic uncertainty. Apollo Global Management Inc and Sixth Street Partners, which had been looking to provide financing for the deal, are no longer in talks with the billionaire entrepreneur, two sources familiar with the matter told Reuters. Shares of the microblogging site were down marginally at $51.12, after rising 20% since Musk this week proposed to go ahead with the A…