[TASK] Raise typo3/testing-framework ^6.8.0

Brings an error/exception handler improvement for
acceptance tests.

composer req --dev typo3/testing-framework:^6.8.0

Resolves: #93735
Releases: master, 10.4
Change-Id: I9d6aff03cd811c36d73959191b946d493ece7572
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/68384


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>