By Valentina Za MILAN (Reuters) -The chairman of Italy’s biggest insurer, Generali, plans to step down in April after 11 years in the job, saying that current tensions among investors were a source of regret. Gabriele Galateri di Genola told the board he would continue as chairman only until a shareholder meeting when investors are due to vote on a new team of directors. His departure comes at a delicate time for Generali, with some influential investors opposed to Philippe Donnet staying on as CEO for another term, although its top shareholder backs him. “I will leave the board in full harmon…