[TASK] Avoid phpunit setLocale()

Deprecated in phpunit 11. Used once.
We remove that test entirely since it
is a direct call to GU::formatSize()
which has its own tests already.

Resolves: #103225
Releases: main
Change-Id: If895a9edd41b3e427ec4eb5751b713cf9da7f017
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/83157


Tested-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>