To disable the lock screen function, set the /apps/panel/global/disable_lock_screen key to true.
When you disable the lock screen function, the following items are removed from the panels:
Lock Screen menu item from the Main Menu.
Lock menu item from the Add to Panel -> Actions menu. To open this menu, right-click on a vacant space on a panel, then choose Add to Panel -> Actions.
Lock Screen menu item from the Actions menu in the Menu Bar
panel application.
Also, any Lock Screen buttons on panels are disabled.