Fix typo in var name that isn't used.

theano/gof/toolbox.py

@@ -333,7 +333,7 @@ class PrintListener(Feature):
 
 class PreserveNames(Feature):
 
-    def on_change_input(self, fgraph, mode, i, r, new_r, reason=None):
+    def on_change_input(self, fgraph, node, i, r, new_r, reason=None):
         if r.name is not None and new_r.name is None:
             new_r.name = r.name