fix doc example - object has no attribute 'lm_logits' (#15143)

Co-authored-by: ydshieh <ydshieh@users.noreply.github.com>

src/transformers/models/openai/modeling_openai.py

@@ -687,7 +687,7 @@ class OpenAIGPTDoubleHeadsModel(OpenAIGPTPreTrainedModel):
         >>> mc_token_ids = torch.tensor([input_ids.size(-1) - 1, input_ids.size(-1) - 1]).unsqueeze(0)  # Batch size 1
 
         >>> outputs = model(input_ids, mc_token_ids=mc_token_ids)
-        >>> lm_logits = outputs.lm_logits
+        >>> lm_logits = outputs.logits
         >>> mc_logits = outputs.mc_logits
         ```"""
         return_dict = return_dict if return_dict is not None else self.config.use_return_dict