Meta Platforms Inc’s second-most powerful executive, Sheryl Sandberg, on Wednesday made the shock announcement that she would leave after a 14-year tenure that included helping steer scandal-prone Facebook to advertising dominance. Sandberg, 52, has been one of the most influential women in Silicon Valley, and her departure comes as the social media juggernaut faces an uncertain future and fierce competition. The chief operating officer’s exit from the Facebook parent would be effective in the fall, she wrote on the platform, adding that she would remain on its board. Among the Silicon Val...