Typo fix (thanks Yuval G.).

Guido van Rossum · Guido van Rossum · commit 108609fc90a4 · 2015-05-26T07:06:28.000-07:00
diff --git a/pep-0484.txt b/pep-0484.txt
@@ -1484,7 +1484,7 @@ example::
   class Node:
       """Binary tree node."""
 
-      def __init__(self, left: Node, right: None):
+      def __init__(self, left: Node, right: Node):
           self.left = left
           self.right = right
 
