[KCM] Improve text for "lock after wake" feature

Summary:
The word "resume" is a technical term that's only clear when suspending is mentioned
in conjunction with it. But we don't use the term "suspend" anymore; we say "sleep."
So its inverse is "wake from sleep".

This patch improves the text according to the above reasoning.

Test Plan:

Reviewers: VDG, GB_2

Reviewed By: VDG, GB_2

Subscribers: plasma-devel

Tags: Plasma

Differential Revision: https://phabricator.kde.org/D22934