Fix warning regarding blur setting
Summary:
There's a bunch of code referring to this setting but not such a setting,
so the qml engine is confused and outputs tons of warnings
Reviewers: Plasma, guoyunhe, ngraham, broulik
Reviewed By: Plasma, broulik
Subscribers: plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D8807