use DefaultAzureCredential instead of AzureCliCredential (#3860)

dotnet/samples/GettingStarted/Agents/Agent_Step03_UsingFunctionTools/Program.cs

@@ -18,9 +18,12 @@ static string GetWeather([Description("The location to get the weather for.")] s
     => $"The weather in {location} is cloudy with a high of 15°C.";
 
 // Create the chat client and agent, and provide the function tool to the agent.
+// 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.
 AIAgent agent = new AzureOpenAIClient(
     new Uri(endpoint),
-    new AzureCliCredential())
+    new DefaultAzureCredential())
     .GetChatClient(deploymentName)
     .AsAIAgent(instructions: "You are a helpful assistant", tools: [AIFunctionFactory.Create(GetWeather)]);