Fix a nit.

Doc/tut/tut.tex

@@ -4413,7 +4413,7 @@ created automatically.
 
 Another key feature is that the local variables and execution state
 are automatically saved between calls.  This made the function easier to write
-and much more clear than an approach using class variables like
+and much more clear than an approach using instance variables like
 \code{self.index} and \code{self.data}.
 
 In addition to automatic method creation and saving program state, when