Resolves: fdo#76905 long delay when changing font size from % to pt

(cherry picked from commit aa16ca73260681b19f0be8a58be95ed454580f7f)

Conflicts:
	svtools/source/control/ctrlbox.cxx

Change-Id: I33d72b51536ab96653ccda64c6e058c497289327
Reviewed-on: https://gerrit.libreoffice.org/8814
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Miklos Vajna <vmiklos@collabora.co.uk>