[BUGFIX] Fix hardcoded icon path in CSS

Resolves: #92977
Releases: master, 10.4
Change-Id: I222f2e7e1f3772d72e0da2b9b77f74cd86852086
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/66967


Tested-by: Markus Klein <markus.klein@typo3.org>
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Marcus Schwemer <ms@schwemer.de>
Tested-by: Oliver Hader <oliver.hader@typo3.org>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Marcus Schwemer <ms@schwemer.de>
Reviewed-by: Oliver Hader <oliver.hader@typo3.org>