[Components][EventDispatcher] Documentation for `EventDispatcher aware Events` is outdated

[SimonSimCity]

As I read through a bunch of my code I saw, that the method $event->getDispatcher() in my event is deprecated as of v2.4 and will be removed in v3.0, even so it's still the only documented way in the current documentation: https://github.com/symfony/symfony-docs/blob/6f286e18acdf003e2f1ced45b202b2578a4a47a6/components/event_dispatcher/introduction.rst#eventdispatcher-aware-events-and-listeners

I browsed through the change-sets on the class and found this one: symfony/event-dispatcher@d855e87

This makes it possible to create a listener like this instead of calling the method $event->getDispatcher():

class LinkRequestListener
{
    public function onKernelRequest(GetResponseEvent $event, $name, EventDispatcherInterface $dispatcher)
    {
    }
}

Please update the documentation, because I don't feel that comfortable with English to write it in a good way :)

[weaverryan]

Thanks for the report Simon! The docs have been fixed for this :).

Cheers!