minor symfony#10673 delete var_dump() functions in examples (JakubSzczesniak)

This PR was submitted for the 4.1 branch but it was merged into the 2.8 branch instead (closes symfony#10673).

Discussion
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delete var_dump() functions in examples

Commits
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04501ea delete var_dump() functions in examples

Author: javiereguiluz

components/event_dispatcher/generic_event.rst

@@ -76,8 +76,6 @@ access the event arguments::
     );
     $dispatcher->dispatch('foo', $event);
 
-    var_dump($event['counter']);
-
     class FooListener
     {
         public function handler(GenericEvent $event)
@@ -97,8 +95,6 @@ Filtering data::
     $event = new GenericEvent($subject, array('data' => 'Foo'));
     $dispatcher->dispatch('foo', $event);
 
-    var_dump($event['data']);
-
     class FooListener
     {
         public function filter(GenericEvent $event)