feat(ChatServices): specify model as 'gpt-4' for improved performance

packages/llm.gblib/services/ChatServices.ts

@@ -302,6 +302,7 @@ export class ChatServices {
         azureOpenAIApiDeploymentName: azureOpenAILLMModel,
         azureOpenAIApiVersion: azureOpenAIVersion,
         temperature: 0,
+        model: 'gpt-4'
         // TODO: callbacks: [logHandler]
       });
     }