Twitter Inc owner Elon Musk on Sunday signaled he would do more to take the social media company in a new direction with a rebranding that will replace its well-known blue bird logo with an X after acknowledging advertisers have been slow to return. The change, which was not evident on the website on Sunday afternoon, followed Musk's recent admission that advertising revenue remains nearly half of what it once was. And Twitter's cash flow has been negative as a result of that and its heavy debt load. "Interim X logo goes live later today," Musk said on Twitter adding…