Steps to reproduce the issue

Update from j6.01 to 6.0.2
Successful update with a warning message.
Warning: Cannot declare class joomla\cms\filesystem\folder, because the name is already in use in /home/wieur/public_html/Joomla_4/libraries/loader.php on line 576

Warning is displayed on almost every page load in back end or front end

Expected result

Actual result

System information (as much as possible)

Joomla 6.0.2
PHP 8.3.29

Additional comments

Related to this issue, applied the fix and confirm it solves the issue
https://issues.joomla.org/tracker/joomla-cms/46300