prefs-dialog: Minor cleanups
Remove AdwActionRow:subtitle-lines
AdwActionRow:subtitle-lines
default value is already 0.
Set use-markup=False in all rows without using a conditional code
Software no longer depends on a libadwaita 1.2 for quite some time, so this conditional code doesn't make sense anymore. Also, set "use-markup=False" in gs-pref-dialog.ui instead.
Edited by Automeris naranja