update os_hardening readme

roles/os_hardening/README.md

@@ -374,11 +374,6 @@ This role is mostly based on guides by:
   - Description: Set to true to disable ctrl-alt-delete key combination.
   - Type: bool
   - Required: no
-- `os_desktop_enable`
-  - Default: `false`
-  - Description: true if this is a desktop system, ie Xorg, KDE/GNOME/Unity/etc.
-  - Type: bool
-  - Required: no
 - `os_env_extra_user_paths`
   - Default: `"[]"`
   - Description: Specify additional paths that should be checked for binaries where access will be minimized