How to disable all Actions sub menus
Download the source, edit it with some source edit tool or IDE (Eclipse, NetBeans), remove the Actions menu from the source, compile and build your own Spark version without that menu. You can then build your own installer or just replace spark.jar file on all computers that you need to remove that menu on. You will have to repeat this process for every new Spark release, if you need some new features or fixes.
There is no option to just disable that menu.