Disable standard actions on VirtualKeyboard SNI
Summary:
We don't want a context-menu entry to quit KWin.
Test Plan: No more context menu shown.
Reviewers: KWin, Plasma on Wayland
Subscribers: plasma-devel, kwin
Tags: Plasma on Wayland, KWin
Differential Revision: https://phabricator.kde.org/D4299