Reduce the number of items we set items/itemsets on the caption, which
reduces the number of times editeng does text layout.

Takes time from 151s to 78s

Change-Id: Iecfb123768fd8f87ffe162b35fe6bcd6b56b8700
Reviewed-on: https://gerrit.libreoffice.org/71359
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>