fix RoleVoter behaviour description

Author: xabbuh

reference/twig_reference.rst

@@ -309,9 +309,8 @@ is_granted
     **type**: ``string``
 
 Returns ``true`` if the current user has the given role. If several roles are
-passed in an array, returns ``true`` if the user has all of them or at least one
-of them, depending on the value of this option:
-:ref:`security.access_decision_manager.strategy <security-voters-change-strategy>`.
+passed in an array, ``true`` is returned if the user has at least one of
+them.
 
 Optionally, an object can be passed to be used by the voter. More information
 can be found in :ref:`security-template`.