[BUGFIX] Fix wrong namespace in test class templates

Change-Id: I561bc7c0b7fd0b2ca8432be1f4af04cc9a269150
Resolves: #54058
Reviewed-on: https://review.typo3.org/25751
Reviewed-by: Oliver Klee
Reviewed-by: Nico de Haen
Tested-by: Nico de Haen