remove unnecessary component mapping 'CustomNavbar'

src/client/js/app.jsx

@@ -15,7 +15,6 @@ import PageComments from './components/PageComments';
 import PageTimeline from './components/PageTimeline';
 import CommentEditorLazyRenderer from './components/PageComment/CommentEditorLazyRenderer';
 import PageManagement from './components/Page/PageManagement';
-import CustomNavbar from './components/CustomNavbar';
 import TrashPage from './components/TrashPage';
 import TrashPageAlert from './components/Page/TrashPageAlert';
 import NotFoundAlert from './components/Page/NotFoundAlert';
@@ -74,8 +73,6 @@ Object.assign(componentMappings, {
 
   'grw-page-status-alert-container': <PageStatusAlert />,
 
-  'custom-nav-bar': <CustomNavbar />,
-
   'trash-page-alert': <TrashPageAlert />,
 
   'trash-page': <TrashPage />,