Remove hello_world example added by React on Rails generator

The hello_world controller, views, and route are not needed as this
tutorial app already has its own example components and routing structure.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: justin808

app/controllers/hello_world_controller.rb

@@ -1,2 +1,4 @@
+// import statement added by react_on_rails:generate_packs rake task
+import "./../generated/server-bundle-generated.js"
 // Server bundle imports
 import serverRegistration from '../bundles/comments/startup/serverRegistration';

app/views/hello_world/index.html.erb

@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 Rails.application.routes.draw do
-  get 'hello_world', to: 'hello_world#index'
   # For details on the DSL available within this file, see http://guides.rubyonrails.org/routing.html
 
   # Serve websocket cable requests in-process