Remove pointless QObject inheritance in model item
Summary:
We don't emit anything or use properties or anything else that requires
MOC. We want to keep model items light.
The emitDataChanged in setRunning still works because that's part of
QStandardItem. Memory management is the same beacuse the
QStandardItemModel takes ownership in appendRow().
Test Plan: Opened widget explorer.
Reviewers: Plasma
Subscribers: plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D4218