BEIJING (Reuters) -China’s ruling Communist Party’s 20th party congress will run for one week from Oct. 16-22 and will amend the party’s constitution, a party spokesman said on Saturday. President Xi Jinping is poised to win a third five-year term as the party’s general secretary at the congress in Beijing and become the most powerful leader since Mao Zedong. The congress will be held in the Great Hall of the People on Tiananmen Square, opening on Sunday and concluding next Saturday, party spokesman Sun Yeli told reporters. Sun said the congress would amend the party’s constitution, but he did…