drm/i1915/guc: Fix probe injection CI failures after recent change

A recent change bumped a 'notice' message up to 'error' level for
debug builds to help trap incorrect configurations in CI systems.
Unfortunately, the error condition in question is triggered by the
error injection probe test. So change the message again to be 'probe
error' level instead.

Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Fixes: 760133d4 ("drm/i915/uc: Make unexpected firmware versions an error in debug builds")
Cc: John Harrison <John.C.Harrison@Intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Alan Previn <alan.previn.teres.alexis@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230510205556.312999-1-John.C.Harrison@Intel.com