Removes the phputf8 library extension (libraries/phputf8 file path).
Testing Instructions
Everything continues working.
Documentation Changes Required
Anyone still including the files from this path can stop. The joomla/string Framework package registers all files which have functionality exposed via the Joomla\String\StringHelper class to the autoloader and if you need something else grab it from libraries/vendor/joomla/string/src/phputf8.
This has already been documented with https://docs.joomla.org/Potential_backward_compatibility_issues_in_Joomla_4#PHPUTF8