LO does its own layouting and also all the scaling, so disable
the automatic HiDPI scaling explicitly. Otherwise fonts will be
rendered in LoDPI and just scaled as an image, if UI scaling is
enabled in KDE, resulting in really blocky / ugly fonts.

Change-Id: I38503ce27c1671e80d0749d21c6c6dcff1a808a6
Reviewed-on: https://gerrit.libreoffice.org/69941
Tested-by: Jenkins
Reviewed-by: Jan-Marek Glogowski <glogow@fbihome.de>