minor #16512 Workflow - Add a note about guards events and ability to save some CPU (kissifrot)

This PR was squashed before being merged into the 5.4 branch.

Discussion
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Workflow - Add a note about guards events and ability to save some CPU

As a follow up of symfony/symfony#45172, I'm adding a note mentioning ability to disable announce events to lower calls in guard events.

Had to add a reference to next paragraph in case it would move elsewhere 🙂

This is my first doc PR so don't hesitate to guide me 🙂

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Commits
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e5c176c Workflow - Add a note about guards events and ability to save some CPU

Author: javiereguiluz

workflow.rst

@@ -509,6 +509,16 @@ missing a title::
 
     The optional second argument of ``setBlocked()`` was introduced in Symfony 5.1.
 
+.. note::
+
+    When using guard listeners which imply intensive workloads (CPU, Database
+    or longer-running code blocks), if you only want them to be fired when strictly
+    necessary (only when ``Workflow::can()`` or ``Workflow::apply()`` is executed),
+    be sure to disable ``Workflow::DISABLE_ANNOUNCE_EVENT`` as indicated in
+    :ref:`Choosing which Events to Dispatch <workflow-chosing-events-to-dispatch>`
+
+.. _workflow-chosing-events-to-dispatch:
+
 Choosing which Events to Dispatch
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~