Convert DLG_ASS to .ui

Change-Id: I29ee55654391f24399aea24fc02c49c430c4e839
Reviewed-on: https://gerrit.libreoffice.org/9834
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>