applets/lock_logout: Restore pre-6.0 UX
Reason for the change
This widget lets you configure what actions are shown, and currently it defaults to showing the "Lock" and "Shut Down" actions. In the past these made sense because Shut Down showed the logout screen with all options, and Lock was the only thing not on the logout screen. So you had the option to access everything.
But in Plasma 6, Shut Down won't show the full logout screen with all options; it now shows only a confirmation-style screen with just Shut Down and Cancel
To restore the old intended UX, let's replace Shut Down with "Show Logout Screen", from which all options can be chosen.
Test plan
Add a new instance of the widget -> it gets the "Show Logout Screen" action by default instead of "Shut Down"
Un-apply the MR, add a new instance of the widget, customize it, apply the MR, and restart Plasma -> prior customizations are saved