minor #7734 Fix missing / (tacman)

This PR was submitted for the 3.2 branch but it was merged into the 2.7 branch instead (closes #7734).

Discussion
----------

Fix missing /

Commits
-------

d323c59 Fix missing /

Author: xabbuh

reference/constraints/Choice.rst

@@ -258,7 +258,7 @@ you can pass the class name and the method as an array.
 
     .. code-block:: php
 
-        // src/AppBundle/EntityAuthor.php
+        // src/AppBundle/Entity/Author.php
         namespace AppBundle\Entity;
 
         use Symfony\Component\Validator\Mapping\ClassMetadata;