Remove visual noise from oox

Change-Id: Ie25838f20f00dc32d9d22959308c118cef688e94
Reviewed-on: https://gerrit.libreoffice.org/8288
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>