fix Qwen Image Transformer single file loading mapping function to be consistent with other loader APIs (#12894)

fix Qwen single file loading to be consistent with other loader API

Author: mbalabanski

src/diffusers/loaders/single_file_model.py

@@ -162,7 +162,7 @@
         "default_subfolder": "transformer",
     },
     "QwenImageTransformer2DModel": {
-        "checkpoint_mapping_fn": lambda x: x,
+        "checkpoint_mapping_fn": lambda checkpoint, **kwargs: checkpoint,
         "default_subfolder": "transformer",
     },
     "Flux2Transformer2DModel": {