Merge pull request #28523 from y-yagi/dont_comment_out_file_watcher_during_rails_upgrade_process

Don't comment out config.file_watcher during Rails upgrade

railties/lib/rails/generators/rails/app/app_generator.rb

@@ -109,8 +109,6 @@ def config_when_updating
 
       config
 
-      gsub_file "config/environments/development.rb", /^(\s+)config\.file_watcher/, '\1# config.file_watcher'
-
       unless cookie_serializer_config_exist
         gsub_file "config/initializers/cookies_serializer.rb", /json(?!,)/, "marshal"
       end

railties/test/generators/app_generator_test.rb

@@ -199,20 +199,6 @@ def test_app_update_set_the_cookie_serializer_to_marshal_if_it_is_not_already_co
     end
   end
 
-  def test_app_update_dont_set_file_watcher
-    app_root = File.join(destination_root, "myapp")
-    run_generator [app_root]
-
-    stub_rails_application(app_root) do
-      generator = Rails::Generators::AppGenerator.new ["rails"], [], destination_root: app_root, shell: @shell
-      generator.send(:app_const)
-      quietly { generator.send(:update_config_files) }
-      assert_file "#{app_root}/config/environments/development.rb" do |content|
-        assert_match(/# config.file_watcher/, content)
-      end
-    end
-  end
-
   def test_app_update_create_new_framework_defaults
     app_root = File.join(destination_root, "myapp")
     run_generator [app_root]