[!!!][TASK] Remove example tasks from EXT:scheduler

The example tasks "sleep" and "test" have been removed.
They were introduced in 2009 when EXT:scheduler was added
to TYPO3 Core.

Kudos to Georg Ringer who brought this up in
https://review.typo3.org/c/Packages/TYPO3.CMS/+/74053

Resolves: #98489
Related: #98453
Related: #11555
Releases: main
Change-Id: I4d9ea99a2a886252dccf86183e72d1d4fd008cc4
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/75927


Tested-by: core-ci <typo3@b13.com>
Tested-by: Chris Müller <typo3@krue.ml>
Tested-by: Benjamin Franzke <bfr@qbus.de>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Chris Müller <typo3@krue.ml>
Reviewed-by: Benjamin Franzke <bfr@qbus.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Benni Mack <benni@typo3.org>