Update JavaScript pack tag expectation in ReactOnRailsHelper spec to defer loading

- Modified the expectation for the JavaScript pack tag in the ReactOnRailsHelper spec to set the `defer` option to true, ensuring scripts are loaded in a non-blocking manner.
- This change improves the performance of the component rendering process in tests.

Author: AbanoubGhadban

spec/dummy/spec/helpers/react_on_rails_helper_spec.rb

@@ -64,7 +64,7 @@ class PlainReactOnRailsHelper
       allow(helper).to receive(:append_stylesheet_pack_tag)
       expect { helper.load_pack_for_generated_component("component_name", render_options) }.not_to raise_error
 
-      expect(helper).to have_received(:append_javascript_pack_tag).with("generated/component_name", { defer: false })
+      expect(helper).to have_received(:append_javascript_pack_tag).with("generated/component_name", { defer: true })
       expect(helper).to have_received(:append_stylesheet_pack_tag).with("generated/component_name")
     end