Twitter stock was falling Friday night after Elon Musk said he is terminating his deal to buy the social media company, asserting that it breached terms of the agreement by refusing to provide detailed information about fake accounts on the site. In a filing that came after the stock market had closed, Musk reported that his lawyers sent a letter to Twitter terminating the deal. In the text of the letter, Musk’s attorney asserted that Twitter had “not complied with its contractual obligation,” and that Musk was therefore ending the deal. The original agreement includes a $1 billion breakup fee,...