Update type.php.twig

Write security context to a variable, so that it can be accessed by anonymous functions like:
```php
<?php
var formOptions = array(
    'query_builder' => function (\Doctrine\ORM\EntityRepository $er) use ($securityContext) {
        return $er->createQueryBuilder('q')
                  ->where('q.user = ?1')
                  ->setParameter(1, $securityContext->getToken()->getUser()->getId());
    }
);
```