tests(mm): fix test for MM, leave the UnknownModelConfig class in the list of configs

Author: psychedelicious

invokeai/backend/model_manager/config.py

@@ -175,7 +175,7 @@ def __init_subclass__(cls, **kwargs):
         if issubclass(cls, LegacyProbeMixin):
             ModelConfigBase.USING_LEGACY_PROBE.add(cls)
         # Cannot use `elif isinstance(cls, UnknownModelConfig)` because UnknownModelConfig is not defined yet
-        elif cls.__name__ != "UnknownModelConfig":
+        else:
             ModelConfigBase.USING_CLASSIFY_API.add(cls)
 
     @staticmethod