Summary: Correct test radiobutton3.qml to use Plasma Components 3 instead of 2.
Test Plan:
Run `qmlscene radiobutton3.qml`
Before:
Misaligned button and big height. (bug in PC2 radiobutton)
After:
Correct height and alignment between button and button's text.
Reviewers: #plasma, davidedmundson
Reviewed By: #plasma, davidedmundson
Subscribers: ngraham, davidedmundson, ndavis, kde-frameworks-devel
Tags: #frameworks, #plasma
Differential Revision: https://phabricator.kde.org/D27082