Revert "Minor, xref link fix. (#35029)" (#35038)

This reverts commit 45d8717.

Author: guardrex

aspnetcore/tutorials/ai-powered-group-chat/ai-powered-group-chat.md

@@ -120,7 +120,7 @@ _history.GetOrAddGroupHistory(groupName, userName, message);
 
 The `CompleteChatStreamingAsync()` method streams responses from OpenAI incrementally, which allows the app to send partial responses to the client as they're generated. 
 
-The code uses a <xref:System.Text.StringBuilder> to accumulate the AI's response. It checks the length of the buffered content and sends it to the clients when it exceeds a certain threshold, for example, 20 characters. This approach ensures that users see the AI’s response as it forms, mimicking a human-like typing effect. 
+The code uses a `StringBuilder` to accumulate the AI's response. It checks the length of the buffered content and sends it to the clients when it exceeds a certain threshold, for example, 20 characters. This approach ensures that users see the AI’s response as it forms, mimicking a human-like typing effect. 
 
 ```csharp
 totalCompletion.Append(content);