Fix usages of Symfony\Bridge\Doctrine\Form\ChoiceList\EntityChoiceList

[aivus]

Symfony\Bridge\Doctrine\Form\ChoiceList\EntityChoiceList deprecated since 2.7 and removed in 3.0

https://github.com/symfony/symfony/blob/2.7/src/Symfony/Bridge/Doctrine/Form/ChoiceList/EntityChoiceList.php#L28-L29

SHFormBundle/Form/Doctrine/ChoiceList/AjaxEntityChoiceList.php

Line 14 in e1fae05

use Symfony\Bridge\Doctrine\Form\ChoiceList\EntityChoiceList;