docs: update vich example to use the Attribute namespace instead (#2250)

Author: cngJo

symfony/file-upload.md

@@ -70,7 +70,7 @@ use Doctrine\ORM\Mapping as ORM;
 use Symfony\Component\HttpFoundation\File\File;
 use Symfony\Component\Serializer\Annotation\Groups;
 use Symfony\Component\Validator\Constraints as Assert;
-use Vich\UploaderBundle\Mapping\Annotation as Vich;
+use Vich\UploaderBundle\Mapping\Attribute as Vich;
 
 #[Vich\Uploadable]
 #[ORM\Entity]