Use the new syntax for prepending the load of twig templates in some Chill*Extension class

src/Bundle/ChillPersonBundle/DependencyInjection/ChillPersonExtension.php

@@ -129,7 +129,7 @@ class ChillPersonExtension extends Extension implements PrependExtensionInterfac
                     'fields' => $config['accompanying_periods_fields'],
                 ],
             ],
-            'form_themes' => ['ChillPersonBundle:Export:ListPersonFormFields.html.twig'],
+            'form_themes' => ['@ChillPerson/Export/ListPersonFormFields.html.twig'],
         ];
         $container->prependExtensionConfig('twig', $twigConfig);