use DefaultAzureCredential instead of AzureCliCredential (#3860)

dotnet/samples/Purview/AgentWithPurview/Program.cs

@@ -24,9 +24,12 @@ TokenCredential browserCredential = new InteractiveBrowserCredential(
         ClientId = purviewClientAppId
     });
 
+// WARNING: DefaultAzureCredential is convenient for development but requires careful consideration in production.
+// In production, consider using a specific credential (e.g., ManagedIdentityCredential) to avoid
+// latency issues, unintended credential probing, and potential security risks from fallback mechanisms.
 using IChatClient client = new AzureOpenAIClient(
     new Uri(endpoint),
-    new AzureCliCredential())
+    new DefaultAzureCredential())
     .GetResponsesClient(deploymentName)
     .AsIChatClient()
     .AsBuilder()