Spencer Platt/Getty Images Citigroup is losing one its three co-heads of mergers and acquisitions. Peter Tague, who served as global co-head of M&A alongside Cary Kochman and Mark Shafir, is leaving Citi, according to a report by Liz Hoffman of The Wall Street Journal. Tague was appointed to the lead M&A role in the 2012. […]