[TASK] Updated docblock for addTcaSelectItem()

Described optional 4th parameter for the $item array, which is used to add
items to defined groups from addTcaSelectItemGroup().

Releases: master
Resolves: #92479
Change-Id: I837c654c90d6e2305558125e697cde5c520bd271
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/66009


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Daniel Haupt <mail@danielhaupt.de>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Daniel Haupt <mail@danielhaupt.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>