Summary: Not needed for normal users with the new edit mode system.

Test Plan: Lock the widgets before compiling this patch. Then compile with it, unlock widgets and see that there is no lock option in the panel context menu.

Reviewers: #plasma, #vdg, ngraham, mart

Reviewed By: #plasma, #vdg, ngraham, mart

Subscribers: broulik, mart, ngraham, #vdg, plasma-devel, #plasma

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D24839