[BUGFIX] Replace wrong method call

There was a wrong call to the new method getFullyQualifiedClassName

Releases: 6.2

Change-Id: Icfac339d107b3e2de7afef6593db7ef9ee47e51a
Reviewed-on: https://review.typo3.org/26788
Reviewed-by: Nico de Haen
Tested-by: Nico de Haen