fix detecting changes in sub-pixel and hinting settings
Summary:
Since D8916, on changes to the sub-pixel and hinting comboboxes the "apply" button stays disabled.
This patch fixes this, so that one can actually apply changes to the font rendering settings.
Test Plan: Open the fonts kcm and change the sub-pixel or hinting settings. The apply button should be enabled.
Reviewers: Plasma, davidedmundson
Reviewed By: Plasma, davidedmundson
Subscribers: plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D11174