docx export: explicitely use 'none' type for disabled cell borders
docx export: explicitely use 'none' type for disabled cell borders

Otherwise, the table default borders will be used.

Change-Id: Iebab1204dc40f79e10164e4815bbdbbe054ef144
Reviewed-on: https://gerrit.libreoffice.org/909
Reviewed-by: Miklos Vajna <16f13092e03e3d9e997de904d0f86cc803fb6ef7@suse.cz>
Tested-by: Miklos Vajna <16f13092e03e3d9e997de904d0f86cc803fb6ef7@suse.cz>

JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core