Had been added as part of 7a8ed362eb "[API CHANGE]
revert and deprecate *BackGraphicURL add *BackGraphic", for no apparent reason.
(Will eventually be added with a "Update the reference rdbs to
libreoffice-6-1-0" commit.)
Change-Id: If6c0405df91accc52a67ad62d7ee7dfb49a4c569
Reviewed-on: https://gerrit.libreoffice.org/53981
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>