message: Update reverse-nodes-in-even-length-groups.py
diff: @@ -28,5 +28,5 @@ class Solution(object):
  curr, last = prev.next, None
  for _ in xrange(cnt):
  curr.next, curr, last = last, curr.next, curr
  - prev.next, prev.next.next, prev = last, curr, prev.next
  + prev.next.next, prev.next, prev = curr, last, prev.next
  return head
  