[Form] Mentioned the change in the "preferred choices" behavior

Author: javiereguiluz

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

@@ -20,6 +20,12 @@ you can list the most popular on top, like Bork Bork and Pirate::
         'preferred_choices' => ['muppets', 'arr'],
     ]);
 
+.. versionadded:: 4.4
+
+    Starting from Symfony 4.4, the preferred choices are displayed both at the
+    top of the list and at their original locations on the list. In prior
+    Symfony versions, they were only displayed at the top of the list.
+
 This options can also be a callback function to give you more flexibility. This might
 be especially useful if your values are objects::