Fix ort documentation code snippet (#2070)

fix code snippet

docs/source/onnxruntime/usage_guides/models.mdx

@@ -13,11 +13,11 @@ Once your model was [exported to the ONNX format](https://huggingface.co/docs/op
 
 ```diff
   from transformers import AutoTokenizer, pipeline
-- from transformers import AutoModelForQuestionAnswering
-+ from optimum.onnxruntime import ORTModelForQuestionAnswering
+- from transformers import AutoModelForCausalLM
++ from optimum.onnxruntime import ORTModelForCausalLM
 
-- model = AutoModelForQuestionAnswering.from_pretrained("meta-llama/Llama-3.2-1B) # PyTorch checkpoint
-+ model = ORTModelForQuestionAnswering.from_pretrained("onnx-community/Llama-3.2-1B", subfolder="onnx") # ONNX checkpoint
+- model = AutoModelForCausalLM.from_pretrained("meta-llama/Llama-3.2-1B) # PyTorch checkpoint
++ model = ORTModelForCausalLM.from_pretrained("onnx-community/Llama-3.2-1B", subfolder="onnx") # ONNX checkpoint
   tokenizer = AutoTokenizer.from_pretrained("meta-llama/Llama-3.2-1B")
 
   pipe = pipeline("text-generation", model=model, tokenizer=tokenizer)
@@ -74,4 +74,4 @@ You can also call `push_to_hub` directly on your model to upload it to the [Hub]
 
 # Push the onnx model to HF Hub
 >>> model.push_to_hub(output_dir, repository_id="my-onnx-repo")  # doctest: +SKIP
-```
+```