fix docstring, this is using _getExtensibleContent, not getDocumentValue

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@22710 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5Type/ExtensibleTraversable.py

@@ -26,7 +26,7 @@ class ExtensibleTraversableMixIn:
     def __bobo_traverse__(self, request, name):
       """
         If no subobject is found through Folder API
-        then try to lookup the object by invoking getDocumentValue
+        then try to lookup the object by invoking _getExtensibleContent
       """
       # Normal traversal
       try: