[TASK] Increase test coverage of GeneralUtility::intExplode()

Just a tiny test change to sort out more details
regarding GeneralUtility::intExplode().

Change-Id: I9df58610ff5b5c79f5b85c13b0ff323f3f988bc3
Resolves: #96811
Releases: main
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/73382


Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Simon Schaufelberger <simonschaufi+typo3@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Simon Schaufelberger <simonschaufi+typo3@gmail.com>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>