[BUGFIX] Fix background of color settings in rtehtmlarea table popup

The color selection of background and text must not be hidden in the popup
of the RTE.

Change-Id: Iae2c7166dcbd441e8491eee038085674ed593dcd
Resolves: #71449
Releases: master
Reviewed-on: https://review.typo3.org/44755


Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>