If you go to the Knowledge Center (sic) Top Level Tab for the Role "SelfServceMobile" there is a section called "Set configuration for fields":
Select the line "Display Name: Filter By Knowledge Type" and then click on Edit.
You will get a pop-up window with the configuration of the Knowledge Article Types:
You can Delete the ones that you do not want to show.
Correct - the solution offered doesn;t work in mobile UI - only removes for desktop UI.
Mobile UI has a lot of restrictions on layout/format changes.