[TASK] Delete acceptance split job files before recreation

The files grow ever larger when repeatedly executing splitAcceptanceTests.php.
Deleting them before they are written for the current run resolves the
problem.

Resolves: #95196
Releases: master, 10.4
Change-Id: I175e486af001307bc99f5879dbc59f9a11c3d69b
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/71038


Tested-by: core-ci <typo3@b13.com>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>