Bristol-Myers Squibb is selling its therapy and surgical care unit, ConvaTec, to two private equity firms, Nordic Capital and Avista Capital Partners for $4.1 billion. The sale, expected to close in the third quarter, is part of the company’s strategy to shift its focus to biopharmaceuticals. This strategy also includes the sale of the company’s medical imaging unit for $525 million, as well as plans to sell between 10% and 20% of its Mead Johnson Nutritional unit.     “Thes...