[!!!][TASK] Drop TCA option showIfRTE for checkboxes

The option showIfRTE on checkboxes did only show up
when the user had the RTE active. This option is removed and
not evaluated anymore in FormEngine.

Resolves: #77592
Releases: master
Change-Id: I0791eb1eb90e3589d41715b798ed631630325c41
Reviewed-on: https://review.typo3.org/49414


Tested-by: Bamboo TYPO3com <info@typo3.com>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Philipp Gampe <philipp.gampe@typo3.org>
Tested-by: Philipp Gampe <philipp.gampe@typo3.org>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>