[TASK] RTE: Store special TCA type configuration in local variable

$this->rte_p is not used at all anymore, and can safely
be removed.

Resolves: #72855
Releases: master
Change-Id: I369296553313c0f21ca5d2e5448ea8d3d8fbf879
Reviewed-on: https://review.typo3.org/46123


Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Morton Jonuschat <m.jonuschat@mojocode.de>
Tested-by: Morton Jonuschat <m.jonuschat@mojocode.de>