[Security] updated CHANGELOG

Author: fabpot

src/Symfony/Component/Security/CHANGELOG.md

@@ -4,6 +4,7 @@ CHANGELOG
 2.1.0
 -----
 
+ * [BC BREAK] The signature of ExceptionListener has changed
  * changed the HttpUtils constructor signature to take a UrlGenerator and a UrlMatcher instead of a Router
  * EncoderFactoryInterface::getEncoder() can now also take a class name as an argument
  * allow switching to the user that is already impersonated