XStyleLoader2 : correct idl description

only implemented for calc at the moment

Change-Id: I7ac631567a69c9ad30da79caad3c50359de14437
Reviewed-on: https://gerrit.libreoffice.org/10923
Reviewed-by: David Tardon <dtardon@redhat.com>
Tested-by: David Tardon <dtardon@redhat.com>