Merge branch '6.4' into 7.1

* 6.4:
  Fix ScheduledStamp FQN

components/messenger.rst

@@ -162,7 +162,7 @@ Here are some important envelope stamps that are shipped with the Symfony Messen
   to configure the validation groups used when the validation middleware is enabled.
 * :class:`Symfony\\Component\\Messenger\\Stamp\\ErrorDetailsStamp`,
   an internal stamp when a message fails due to an exception in the handler.
-* :class:`Symfony\\Component\\Messenger\\Stamp\\ScheduledStamp`,
+* :class:`Symfony\\Component\\Scheduler\\Messenger\\ScheduledStamp`,
   a stamp that marks the message as produced by a scheduler. This helps
   differentiate it from messages created "manually". You can learn more about it
   in the :doc:`Scheduler documentation </scheduler>`.