minor #16300 [EventDispatcher] fix docblock (xabbuh)

This PR was merged into the 2.8 branch.

Discussion
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[EventDispatcher] fix docblock

| Q             | A
| ------------- | ---
| Fixed tickets | https://github.com/symfony/symfony/pull/16198#discussion_r41857529
| License       | MIT

Commits
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6e515fb [EventDispatcher] fix docblock

src/Symfony/Component/EventDispatcher/EventDispatcher.php

@@ -81,7 +81,7 @@ class EventDispatcher implements EventDispatcherInterface
      * Returns null if the event or the listener does not exist.
      *
      * @param string   $eventName The name of the event
-     * @param callable $listener  The listener to remove
+     * @param callable $listener  The listener
      *
      * @return int|null The event listener priority
      */