minor #16634 Use a better name than "class Foo" (BafS)

This PR was submitted for the 5.4 branch but it was merged into the 4.4 branch instead.

Discussion
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Use a better name than "class Foo"

It took me a while to figure out what represent `class Foo`

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Commits
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1b8d52d Use a better name than "class Foo"

Author: javiereguiluz

components/event_dispatcher.rst

@@ -499,9 +499,9 @@ is dispatched, are passed as arguments to the listener::
     use Symfony\Contracts\EventDispatcher\Event;
     use Symfony\Contracts\EventDispatcher\EventDispatcherInterface;
 
-    class Foo
+    class MySubscriber
     {
-        public function myEventListener(Event $event, $eventName, EventDispatcherInterface $dispatcher)
+        public function myEventListener(Event $event, string $eventName, EventDispatcherInterface $dispatcher)
         {
             // ... do something with the event name
         }