Switch to the old-style button text for the KNSQuick buttons

Summary:
This fixes a series of localization issues as reported in
https://bugs.kde.org/show_bug.cgi?id=415541 based on the
minimum-impact method (hopefully these strings should even
still be in the pot files...)

BUG:415541

Reviewers: #plasma, davidedmundson

Reviewed By: #plasma, davidedmundson

Subscribers: aacid, yurchor, davidedmundson, kde-i18n-doc, gikari, plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D26892