docs(mm): add comment in move_model_to_device

Author: psychedelicious

invokeai/backend/model_manager/load/model_cache/model_cache_default.py

@@ -261,6 +261,7 @@ def move_model_to_device(self, cache_entry: CacheRecord[AnyModel], target_device
         if torch.device(source_device).type == torch.device(target_device).type:
             return
 
+        # Some models don't have a `to` method, in which case they run in RAM/CPU.
         if not hasattr(cache_entry.model, "to"):
             return