Reduce unneeded dependencies

Summary:
No need to translate a test app that is not even being installed.
Make it a QGuiApplication so less stuff is pulled.

Test Plan: Still crashes :)

Reviewers: #frameworks, davidedmundson, sitter

Reviewed By: davidedmundson, sitter

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D28061