[TASK] Raise typo3/testing-framework to ^6.6.0

Makes lit-html loadable in unit tests.

composer require --dev typo3/testing-framework ^6.6.0

Change-Id: I4b5cbf0825d12708882e744b10ffa31b78332c25
Resolves: #93074
Releases: master, 10.4
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/67113


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Benjamin Franzke <bfr@qbus.de>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Benjamin Franzke <bfr@qbus.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>