[TASK] Hide selected items in multipleSideBySide

If a multipleSideBySide form element is not allowed to add the same
value multiple times, its selected values are hidden now and it's not
possible to add them again unless the values are removed from the
selection.

Resolves: #76071
Releases: master, 7.6
Change-Id: I99d6c609ca081f4b8cb6f8ad07f74385a23b7a5c
Reviewed-on: https://review.typo3.org/48031


Reviewed-by: Nicole Cordes <typo3@cordes.co>
Tested-by: Nicole Cordes <typo3@cordes.co>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>