[!!!][TASK] Remove RTE "modes" option in TCA

It's ts_css anyways all the time through the overruleMode
option, which should be used anyway for the time being (as this option
still exists).

Resolves: #72856
Releases: master
Change-Id: If96f1c0faddf9b258fa3a60f4904cd48eb3ca854
Reviewed-on: https://review.typo3.org/46122


Reviewed-by: Frank Nägler <frank.naegler@typo3.org>
Tested-by: Frank Nägler <frank.naegler@typo3.org>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>