fix: Replace dead link for Densenet (#8394)

Author: yinggeh

docs/user_guide/performance_tuning.md

@@ -187,8 +187,8 @@ other frameworks.
 mkdir -p ./models/densenet_onnx/1
 
 # Download model and place it in model repository
-wget -O models/densenet_onnx/1/model.onnx
-https://contentmamluswest001.blob.core.windows.net/content/14b2744cf8d6418c87ffddc3f3127242/9502630827244d60a1214f250e3bbca7/08aed7327d694b8dbaee2c97b8d0fcba/densenet121-1.2.onnx
+wget -O models/densenet_onnx/1/model.onnx \
+    https://github.com/onnx/models/raw/main/validated/vision/classification/densenet-121/model/densenet-7.onnx
 ```
 
 2. Create a minimal [Model Configuration](model_configuration.md) for the