[!!!][TASK] Remove support for instantiating IconRegistry in ext_loca… (#5038)

* [!!!][TASK] Remove support for instantiating IconRegistry in ext_localconf.php

Resolves: TYPO3-Documentation/Changelog-To-Doc#1122
Releases: main

* Apply suggestions from code review

Co-authored-by: Sandra Erbel <Alagts@users.noreply.github.com>

---------

Co-authored-by: Sandra Erbel <Alagts@users.noreply.github.com>

Author: linawolf

Documentation/ApiOverview/Icon/Index.rst

@@ -24,14 +24,13 @@ To register icons for your own extension, create a file called
 :file:`Configuration/Icons.php` in your extension - for example:
 :file:`EXT:my_extension/Configuration/Icons.php`.
 
-..  note::
-    In versions below TYPO3 v11.4 the configuration was done in the
+..  versionchanged:: 14.0
+    It is not possible anymore to register icons in the
     :file:`ext_localconf.php` file.
 
-    It :ref:`migrates the icon registration <icon_migration>` to
+    :ref:`Migrate the icon registration <icon_migration>` to
     new format. There is also a Rector rule.
 
-
 The file needs to return a PHP configuration array with the following keys:
 
 ..  literalinclude:: _Icons.php