NEW YORK (Reuters) -Billionaire Elon Musk was sued by Twitter Inc investors for delayed disclosure of his stake in the company, as the owner of electric carmaker Tesla Inc mounts a $44 billion takeover bid for the social media platform. The investors said Musk saved himself $156 million by failing to disclose that he had purchased more than 5% of Twitter by March 14. He continued to buy stock after that, and ultimately disclosed in early April that he owned 9.2% of the company, according to the lawsuit, filed on Wednesday in San Francisco federal court. “By delaying his disclosure of his stake…