[DOCS] Fix scheduler garbage collection task example

Existing configuration should not be overwritten
when adding new table options.

Releases: master
Resolves: #95019
Change-Id: Ie45619e9539e055ef99af1d7cec8cb80b6ed8bde
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/70802


Tested-by: Benjamin Franzke <bfr@qbus.de>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Benjamin Franzke <bfr@qbus.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>