Update face sample url.

Author: bojunehsu

articles/ai-services/content-understanding/face/overview.md

@@ -92,4 +92,4 @@ Azure AI Content Understanding adheres to Microsoft's strict policies on custome
 ## Next steps
 
 * Learn how to build a [**person directory**](../tutorial/build-person-directory.md).
-* Review code sample: [**person directory**](https://github.com/Azure-Samples/azure-ai-content-understanding-python/blob/zhizho/face/notebooks/build_person_directory.ipynb).
+* Review code sample: [**person directory**](https://github.com/Azure-Samples/azure-ai-content-understanding-python/blob/main/notebooks/build_person_directory.ipynb).