Closes #12036: ConfigParser: Document items() added the vars dictionary to the result

Author: ambv

Doc/library/configparser.rst

@@ -1064,6 +1064,11 @@ ConfigParser Objects
       given *section*.  Optional arguments have the same meaning as for the
       :meth:`get` method.
 
+      .. versionchanged:: 3.2
+
+         Items present in *vars* no longer appear in the result. The previous
+         behaviour mixed actual parser options with variables provided for
+         interpolation.
 
    .. method:: set(section, option, value)