[DOCS] Add correct indentations in rte_ckeditor documentation

This patch takes the changes of the new documentation
theme into account.

Releases: master, 9.5
Resolves: #91102
Change-Id: I3308819227dc4a66f0571e4b5afdc49939f19026
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/64223


Tested-by: Jonas Eberle <flightvision@googlemail.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Björn Jacob <bjoern.jacob@tritum.de>
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Oliver Hader <oliver.hader@typo3.org>
Reviewed-by: Jonas Eberle <flightvision@googlemail.com>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Björn Jacob <bjoern.jacob@tritum.de>
Reviewed-by: Oliver Hader <oliver.hader@typo3.org>