[!!!][TASK] Removed deprecated code from EXT:rtehtmlarea

Releases: master
Resolves: #72390
Change-Id: I6979f4289ebcb5a1027dbc5996e53ad3f70669c8
Reviewed-on: https://review.typo3.org/45408


Reviewed-by: Daniel Goerz <ervaude@gmail.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>