Fix `ConditionalDetrForSegmentation` doc example (#20531)

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

src/transformers/models/conditional_detr/modeling_conditional_detr.py

@@ -1884,7 +1884,7 @@ class ConditionalDetrForSegmentation(ConditionalDetrPreTrainedModel):
         ...     ConditionalDetrConfig,
         ...     ConditionalDetrForSegmentation,
         ... )
-        >>> from transformers.models.conditional_detr.feature_extraction_conditional_detr import rgb_to_id
+        >>> from transformers.image_transforms import rgb_to_id
 
         >>> url = "http://images.cocodataset.org/val2017/000000039769.jpg"
         >>> image = Image.open(requests.get(url, stream=True).raw)