drop XPersistObject support from SvNumberFormatsSupplierService

why should css.util.NumberFormatsSupplier support XPersistObject and need
read/write support ?

Change-Id: I62bc2fa3a0adef6cf5b7006f4e2bf3a9a157043d
Reviewed-on: https://gerrit.libreoffice.org/12281
Reviewed-by: Eike Rathke <erack@redhat.com>
Tested-by: Eike Rathke <erack@redhat.com>