CHESTER, PA.—Sean Johnson high-stepped his way up the stairs at the back of a makeshift stage as his New York City FC teammates parted to let the standout goalie slide through the gap. He crouched and then burst straight up with the MLS Eastern Conference championship trophy as New York danced and shook the floor with good reason—a shot at its first championship is on deck. Talles Magno scored in the 88th minute to send New York into the MLS Cup final with a 2–1 win over the COVID-19-restriction-ravaged Philadelphia Union on Sunday. New York will play at the Portland Timbers on Saturday for the MLS Cup. “This team, they don’t stop,” coach Ronny Deila said. “They keep on going. Now we are in the final, so we’re going to be ready.” Gudi Thórarinsson stripped the ball from Union defender Olivier Mbaizo and fed it to Magno for the decisive …