minor symfony#14492 update obsolete PHP callable docs link (0xb4lamx)

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

Discussion
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update obsolete `PHP callable` docs link

new `PHP callable` link https://www.php.net/manual/en/language.types.callable.php

Commits
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0d182b3 update PHP callable docs link

Author: javiereguiluz

components/event_dispatcher.rst

@@ -532,4 +532,4 @@ Learn More
 .. _Mediator: https://en.wikipedia.org/wiki/Mediator_pattern
 .. _Observer: https://en.wikipedia.org/wiki/Observer_pattern
 .. _Closures: https://www.php.net/manual/en/functions.anonymous.php
-.. _PHP callable: https://www.php.net/manual/en/language.pseudo-types.php#language.types.callback
+.. _PHP callable: https://www.php.net/manual/en/language.types.callable.php