Set React to Strict Mode

Set React to Strict Mode.

See: https://reactjs.org/docs/strict-mode.html

awx/ui_next/src/index.jsx

@@ -7,6 +7,8 @@ import { BrandName } from './variables';
 document.title = `Ansible ${BrandName}`;
 
 ReactDOM.render(
-  <App />,
+  <React.StrictMode>
+    <App />
+  </React.StrictMode>,
   document.getElementById('app') || document.createElement('div')
 );

awx/ui_next/src/index.test.jsx

@@ -12,6 +12,11 @@ require('./index.jsx');
 
 describe('index.jsx', () => {
   it('renders ok', () => {
-    expect(ReactDOM.render).toHaveBeenCalledWith(<App />, div);
+    expect(ReactDOM.render).toHaveBeenCalledWith(
+      <React.StrictMode>
+        <App />
+      </React.StrictMode>,
+      div
+    );
   });
 });