.Net: Refactor kernel initialization in Step01_Agent (#12181)

This pull request updates the `UseSingleChatCompletionAgent` method in
`Step01_Agent.cs` to improve code clarity and reusability. The most
important change is replacing the call to
`CreateKernelWithChatCompletion()` with the existing `kernel` parameter.

Code clarity and reusability:

*
[`dotnet/samples/GettingStartedWithAgents/Step01_Agent.cs`](diffhunk://#diff-406533ddffa54164a374596ac14a8eb4f1b07ed75f8a235d349c4086cc69dbc5L36-R36):
Updated the `Kernel` property to use the `kernel` parameter instead of
calling `CreateKernelWithChatCompletion()`. This change removes
redundancy and simplifies the method.

Co-authored-by: Chris <[email protected]>
Co-authored-by: Mark Wallace <[email protected]>

Author: 3 people

dotnet/samples/GettingStartedWithAgents/Step01_Agent.cs

@@ -27,15 +27,15 @@ public class Step01_Agent(ITestOutputHelper output) : BaseAgentsTest(output)
     [InlineData(false)]
     public async Task UseSingleChatCompletionAgent(bool useChatClient)
     {
-        Kernel kernel = this.CreateKernelWithChatCompletion();
+        Kernel kernel = this.CreateKernelWithChatCompletion(useChatClient, out var chatClient);
 
         // Define the agent
         ChatCompletionAgent agent =
             new()
             {
                 Name = ParrotName,
                 Instructions = ParrotInstructions,
-                Kernel = this.CreateKernelWithChatCompletion(useChatClient, out var chatClient),
+                Kernel = kernel
             };
 
         // Respond to user input