Successor: Expected file name works with Python, too :)

01-tree_successor/task.md

@@ -7,4 +7,4 @@ and it should return another node of the tree with the next higher key
 - The given node can also be a null pointer, in which case the method should
   return the smallest node in the tree.
 
-You should submit the file `tree_successor.h`.
+You should submit the file `tree_successor.*`.