Rename ScFilterDescriptorBaseObj to ScFilterDescriptorBase so it
matches the object name we test against.

Change-Id: Ia5ce59997e99b2b537e50ddfeaa9d96b2b55555f
Reviewed-on: https://gerrit.libreoffice.org/67033
Tested-by: Jenkins
Reviewed-by: Jens Carl <j.carl43@gmx.de>