[BUGFIX] Wrong namespace in functional test of FluidTemplate cObject

Resolves: #56816
Releases: 6.2
Change-Id: I3abed35a5e27bdc9db2b18d5caa13681ef5a9305
Reviewed-on: https://review.typo3.org/28294
Reviewed-by: Wouter Wolters
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn