Point out what is deprecated

Grégoire Paris · Grégoire Paris · commit 0ac65bb32d7a · 2012-11-27T10:03:02.000+01:00
diff --git a/reference/forms/types/options/property_path.rst.inc b/reference/forms/types/options/property_path.rst.inc
@@ -11,7 +11,9 @@ you can set the ``property_path`` option. Its default value is the field's
 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``
+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:
 
 .. versionadded:: 2.1
     Since 2.1, the ``mapped`` option has been added for this use-case
