CHARLESTON, S.C. — South Carolina’s Senate passed legislation Tuesday to remove the Confederate battle flag from the state house, where it has flown for five decades despite being viewed by many as a symbol of slavery.A bill to banish the flag from the Capitol grounds to a museum easily passed a third and final vote in the Senate by a 36-3 margin and is now headed for debate in the state’s House of Representatives.The legislation, deemed a non-starter only months ago, has garnered strong bipartisan support after the June 17 killings of nine African-American churchgoers during Bible study at Emanuel African Methodist Episcopal church in the port city of Charleston, about two hours south of the state capital Columbia.