minor #12643 ContainerAwareEventDispatcher was removed (makmaoui)

This PR was merged into the 4.3 branch.

Discussion
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ContainerAwareEventDispatcher was removed

ContainerAwareEventDispatcher was removed in Symfony 4.0

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Commits
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ac84bfb ContainerAwareEventDispatcher was removed

Author: xabbuh

components/event_dispatcher.rst

@@ -469,7 +469,6 @@ Other Dispatchers
 Besides the commonly used ``EventDispatcher``, the component comes
 with some other dispatchers:
 
-* :doc:`/components/event_dispatcher/container_aware_dispatcher`
 * :doc:`/components/event_dispatcher/immutable_dispatcher`
 * :doc:`/components/event_dispatcher/traceable_dispatcher`