Corrected typo in error_pages.rst

Removed extra comma before "event" word.

Author: askeita

controller/error_pages.rst

@@ -319,7 +319,7 @@ error pages.
 .. note::
 
     If your listener calls ``setThrowable()`` on the
-    :class:`Symfony\\Component\\HttpKernel\\Event\\ExceptionEvent`,
+    :class:`Symfony\\Component\\HttpKernel\\Event\\ExceptionEvent`
     event, propagation will be stopped and the response will be sent to
     the client.