kcms: translations: use availableDomainTranslations from plasmashell instead of systemsettings
Summary: The kcm might be used with different settings apps like plasma-settings, in that case systemsettings is not installed.
Reviewers: hein
Reviewed By: hein
Subscribers: bshah, hein, plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D22503