By Michael Martina, Daphne Psaledakis and David Brunnstrom WASHINGTON (Reuters) – With a wary eye on China, President Joe Biden announced an agreement aimed at bolstering trade ties between the United States and Africa on Wednesday after years in which the continent took a back seat to other U.S. priorities. “The United States is ‘all in’ on Africa’s future,” Biden told African leaders attending a three-day summit in Washington. Biden’s remarks, and the summit, aim to show that the United States is a better partner for Africa than China, which has sought to expand its influence by funding infr…