drm/xe/guc: Remove obsolete GuC CTB documentation

Refer to already described CTB Descriptor and CTB HXG Message.

Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://lore.kernel.org/r/20231128203203.1147-2-michal.wajdeczko@intel.com


Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>