symfony#15331 add infos about deprecated classes to UPGRADE-3.0

Author: vincentaubert

UPGRADE-3.0.md

@@ -272,6 +272,17 @@ UPGRADE FROM 2.x to 3.0
    ```php
    echo $form->getErrors(true, false);
    ```
+   * The `Symfony\Component\Form\Extension\Core\ChoiceList\ChoiceList` class has been removed in
+     favor of `Symfony\Component\Form\ChoiceList\ArrayChoiceList`.
+
+   * The `Symfony\Component\Form\Extension\Core\ChoiceList\LazyChoiceList` class has been removed in
+     favor of `Symfony\Component\Form\ChoiceList\LazyChoiceList`.
+
+   * The `Symfony\Component\Form\Extension\Core\ChoiceList\ObjectChoiceList` class has been removed in
+     favor of `Symfony\Component\Form\ChoiceList\ArrayChoiceList`.
+
+   * The `Symfony\Component\Form\Extension\Core\ChoiceList\SimpleChoiceList` class has been removed in
+     favor of `Symfony\Component\Form\ChoiceList\ArrayChoiceList`.
 
 ### FrameworkBundle