Added and fixed gettext usage for better translation coverage. Fixes #5284

1) Fixed usage gettext('') instead of _('') in javascript files.
  2) Fixed usage gettext('') instead of `${gettext('')}` in javascript files,
     because "pybabel extract" not support extracting from this syntax.

web/pgadmin/misc/dependents/static/js/dependents.js

@@ -76,7 +76,7 @@ define('misc.dependents', [
       var $container = this.dependentsPanel.layout().scene().find('.pg-panel-content'),
         $gridContainer = $container.find('.pg-panel-dependents-container'),
         grid = new Backgrid.Grid({
-          emptyText: 'No data found',
+          emptyText: gettext('No data found'),
           columns: [{
             name: 'type',
             label: gettext('Type'),