migrate projects:boards:* to static bundle

app/assets/javascripts/dispatcher.js

@@ -49,13 +49,6 @@ import SearchAutocomplete from './search_autocomplete';
       });
 
       switch (page) {
-        case 'projects:boards:show':
-        case 'projects:boards:index':
-          import('./pages/projects/boards')
-            .then(callDefault)
-            .catch(fail);
-          shortcut_handler = true;
-          break;
         case 'projects:environments:metrics':
           import('./pages/projects/environments/metrics')
             .then(callDefault)

app/assets/javascripts/pages/projects/boards/index.js

 import UsersSelect from '~/users_select';
 import ShortcutsNavigation from '~/shortcuts_navigation';
 
-export default () => {
+document.addEventListener('DOMContentLoaded', () => {
   new UsersSelect(); // eslint-disable-line no-new
   new ShortcutsNavigation(); // eslint-disable-line no-new
-};
+});