[BUGFIX] EXT:Scheduler: Adjust return type of convertRangeToListOfValues

Resolves: #79086
Releases: master
Change-Id: I47e77f5bc8915d972bd9c19fe8c95f77aea4be7f
Reviewed-on: https://review.typo3.org/51038


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: Andreas Fernandez <typo3@scripting-base.de>
Reviewed-by: Morton Jonuschat <m.jonuschat@mojocode.de>
Tested-by: Morton Jonuschat <m.jonuschat@mojocode.de>