ACCRA, GHANA — Ghana’s ruling New Patriotic Party candidate, Vice President Mahamudu Bawumia, on Sunday conceded defeat in the country’s presidential election after failing to shake off widespread frustration over the struggling economy. Defeat in Saturday’s election ended two terms in power for the NPP under President Nana Akufo-Addo, marked by Ghana’s worst economic crisis in years, high inflation and a debt default. “The people of Ghana have spoken, the people have voted for change at this time and we respect it with all humility,” Bawumia said in a news conference. Bawumia said he had called his opponent, National Democratic