Update an example to match current output.

Doc/lib/libdis.tex

@@ -26,9 +26,7 @@ the following command can be used to get the disassembly of
   2           0 LOAD_GLOBAL              0 (len)
               3 LOAD_FAST                0 (alist)
               6 CALL_FUNCTION            1
-              9 RETURN_VALUE        
-             10 LOAD_CONST               0 (None)
-             13 RETURN_VALUE
+              9 RETURN_VALUE
 \end{verbatim}
 
 (The ``2'' is a line number).