Fix QFontMetrics::width() deprecation warning by switching to boundingRect().width()
Summary:
According to an article by @cfeck [1], QFontMetrics::width() gave the horizontal advance, which doesn't necessarily include every pixel that the text might use.
He suggested that boundingRect().width() might be what most people actually want.
Reviewers: Breeze, Plasma, davidedmundson
Reviewed By: Plasma, davidedmundson
Subscribers: hpereiradacosta, cfeck, plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D26270