Show banner only to admin users, use JS bundle to handle dismiss

app/views/layouts/header/_default.html.haml

-- if license_message.present?
-  .alert.alert-dismissible.gitlab-ee-trial-banner.js-gitlab-ee-trial-banner{ role: 'alert' }
+- if current_user.admin? && license_message.present?
+  .alert.alert-dismissible.gitlab-ee-trial-banner.hidden.js-gitlab-ee-trial-banner{ role: 'alert', 'data-license-expiry' => current_license.expires_at }
     %button.close{ type: 'button', 'data-dismiss' => 'alert', 'aria-label' => 'Dismiss banner' }
       = icon('times', 'aria-hidden' => 'true')
     %p
       = license_message
-  :javascript
-    $('.js-gitlab-ee-trial-banner').on('close.bs.alert', function() { $('.js-navbar-gitlab').removeClass('has-trial-banner'); });
-%header.navbar.navbar-gitlab.js-navbar-gitlab{ class: "#{nav_header_class} #{ 'has-trial-banner' if trial_license_message.present?}" }
+%header.navbar.navbar-gitlab.js-navbar-gitlab{ class: "#{nav_header_class}" }
   .navbar-border
   %a.sr-only.gl-accessibility{ href: "#content-body", tabindex: "1" } Skip to content
   .container-fluid