Yahoo co-founder Jerry Yang is leaving the struggling Internet company, as it tries to revive its revenue growth and win over disgruntled shareholders under a new leader.The departure, announced Tuesday, punctuates the end of an era at Yahoo, a tarnished Internet icon that has spent much of the last decade scrambling to catch up to Internet search leader Google Inc. a company that got early encouragement and advice from Yang. It comes just two weeks after Yahoo Inc. hired former PayPal executive Scott Thompson as its CEO.