chore: update app environment to demo

- Change appEnvironment from production to demo in main.dart

Author: fulleni

lib/main.dart

@@ -6,7 +6,7 @@ import 'package:flutter_news_app_mobile_client_full_source_code/app/services/spl
 import 'package:flutter_news_app_mobile_client_full_source_code/bootstrap.dart';
 
 // Define the current application environment (production/development/demo).
-const appEnvironment = AppEnvironment.production;
+const appEnvironment = AppEnvironment.demo;
 
 void main() async {
   final appConfig = switch (appEnvironment) {