(Reuters) -Meta Platforms Inc Chief Operating Officer Sheryl Sandberg, whose close partnership with Chief Executive Officer Mark Zuckerberg powered the growth of the world’s biggest social network, is leaving the company after 14 years, she said in a Facebook post on Wednesday. Her announcement sent the social media firm’s shares down 4%. Sandberg is one of the most visible executives at Meta and has long been a staunch defender of the company’s often-criticized business model and its founder, Zuckerberg. “When I took this job in 2008, I hoped I would be in this role for five years. Fourteen y…