For the fourth time in as many games in the National League Championship Series, the Mets tallied first, and they didn’t let up, posting an 8-3 victory over the Cubs on Wednesday night at Wrigley Field to complete a sweep and reach the World Series for the first time since 2000. New York will face the winner of the Royals-Blue Jays American League Championship Series, which the Royals lead, 3-2.