For Table of Figures/Objects/Tables.
Make this similar to DOCX: only one source style is possible, so omit
the intermediate text:index-source-styles element.
Also a boolean attribute like text:use-index-source-styles appears as
unnecessary complexity, so try to do without.
Change-Id: I7cb599c7ec1261ddedc196a25c3eafe35f35fbe9
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/146013
Tested-by: Jenkins
Reviewed-by: Michael Stahl <michael.stahl@allotropia.de>
90e1698dab