WASHINGTON — Twitter’s acceptance of Elon Musk’s roughly $44 billion takeover bid brings the billionaire Tesla CEO one step closer to owning the social media platform. The deal is expected to close sometime this year. But before that, shareholders still have to weigh in, as well as regulators in the U.S. and in countries where Twitter does business, before the deal is completed. Questions also remain about what exactly could change about the platform. Musk has not released an official list of changes, but he has expressed interest in a number of updates.