Adding two forgotten use statements to virtual form cookbook page

Author: Jake Bell

cookbook/form/use_virtuals_forms.rst

@@ -50,6 +50,7 @@ Start by creating a very simple ``CompanyType`` and ``CustomerType``::
     // src/Acme/HelloBundle/Form/Type/CompanyType.php
     namespace Acme\HelloBundle\Form\Type;
 
+    use Symfony\Component\Form\AbstractType;
     use Symfony\Component\Form\FormBuilderInterface;
 
     class CompanyType extends AbstractType
@@ -85,6 +86,7 @@ location form type::
     // src/Acme/HelloBundle/Form/Type/LocationType.php
     namespace Acme\HelloBundle\Form\Type;
 
+    use Symfony\Component\Form\AbstractType;
     use Symfony\Component\Form\FormBuilderInterface;
     use Symfony\Component\OptionsResolver\OptionsResolverInterface;