drm/xe/snapshot: Remove drm_err on guc alloc failures

The kernel will complain loudly if allocation fails, no need to do it
ourselves.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Francois Dugast <francois.dugast@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240221133024.898315-1-maarten.lankhorst@linux.intel.com