[TASK] Remove unused iconRegistry in CheckboxToggleElement

Resolves: #94795
Releases: master
Change-Id: Ia4a0123a70a2b50b4f89e04e3f15c18559489c97
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/70438


Tested-by: core-ci <typo3@b13.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Oliver Bartsch <bo@cedev.de>