use admin's translation domain for delete checkbox

otherwise it's in messages ...

Form/Type/AdminType.php

@@ -31,7 +31,7 @@ class AdminType extends AbstractType
         $admin = $this->getAdmin($options);
 
         if ($options['delete'] && $admin->isGranted('DELETE')) {
-            $builder->add('_delete', 'checkbox', array('required' => false, 'mapped' => false));
+            $builder->add('_delete', 'checkbox', array('required' => false, 'mapped' => false, 'translation_domain' => $admin->getTranslationDomain()));
         }
 
         if (!$admin->hasSubject()) {