Update the type of tp_dealloc.

Doc/ext/newtypes.tex

@@ -347,7 +347,7 @@ will implement.
 \index{finalization, of objects}
 
 \begin{verbatim}
-    destructor tp_dealloc;
+    freefunc tp_dealloc;
 \end{verbatim}
 
 This function is called when the reference count of the instance of