[BUGFIX] Avoid double CSH wraps in linkvalidator tasks settings

Labels in linkvalidator's additional field settings for the schedule
are actually invoking `BackendUtility::wrapInHelp` twice - first time
in `ValidatorTaskAdditionalFieldProvider` and second time when actually
rendering with `f:be.labels.csh` view-helper.

Resolves: #92964
Releases: master, 10.4, 9.5
Change-Id: I8dc5baca7289604a150e2d80258fb21ebab9f59e
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/67549


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Sybille Peters <sypets@gmx.de>
Tested-by: Richard Haeser <richard@richardhaeser.com>
Reviewed-by: Helmut Hummel <typo3@helhum.io>
Reviewed-by: Richard Haeser <richard@richardhaeser.com>