reference/.../property_path : Minor fix, suggest to use 'mapped' option ...

... the explanation was not complete

Author: gregquat

reference/forms/types/options/property_path.rst.inc

@@ -12,8 +12,8 @@ name.
 
 If you wish the field to be ignored when reading or writing to the object 
 you can set the ``property_path`` option to ``false``, but using
-``property_path`` for this purpose is deprecated, you should do it the way
-described below:
+``property_path`` for this purpose is deprecated, you should use the
+``mapped`` option.
 
 .. versionadded:: 2.1
     Since 2.1, the ``mapped`` option has been added for this use-case.