Update security.rst

Propose attribute usage instead of annotations, this stick more to the example.

Author: ffouillet

security.rst

@@ -2148,7 +2148,7 @@ will happen:
 .. _security-securing-controller-annotations:
 
 Thanks to the SensioFrameworkExtraBundle, you can also secure your controller
-using annotations:
+using attributes:
 
 .. configuration-block::