drm/xe/uapi: Remove XE_QUERY_CONFIG_FLAGS_USE_GUC

This config is the only real one. If execlist remains in the
code it will forever be experimental and we shouldn't maintain
an uapi like that for that experimental piece of code that
should never be used by real users.

Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>