Update webdriver.py

Start_y - y-coordinate for start, not end

Author: urtow

appium/webdriver/webdriver.py

@@ -226,7 +226,7 @@ def swipe(self, start_x, start_y, end_x, end_y, duration=None):
 
         :Args:
          - start_x - x-coordinate at which to start
-         - start_y - y-coordinate at which to end
+         - start_y - y-coordinate at which to start
          - end_x - x-coordinate at which to stop
          - end_y - y-coordinate at which to stop
          - duration - (optional) time to take the swipe, in ms.