President Xi Jinping of China, traveling to Africa for the first time in five years, pledged greater cooperation with South Africa to enhance the voice of poor nations. He commended developing countries for “shaking off the yoke of colonialism.” And on Wednesday, he’s expected to hold talks with the leaders of the BRICS, a club of emerging nations, as he pushes for its expansion to serve as a counterweight to Western dominance. On his four-day visit to South Africa this week, Mr. Xi has sought to cast himself as a…