fix tabs for bootstrap 4

app/views/projects/clusters/new.html.haml

@@ -3,19 +3,18 @@
 - active_tab = local_assigns.fetch(:active_tab, 'new')
 = javascript_include_tag 'https://apis.google.com/js/api.js'
 
-
 = render_gcp_signup_offer
 
 .row.prepend-top-default
   .col-sm-3
     = render 'sidebar'
   .col-lg-9.js-toggle-container
-    %ul.nav-links.gitlab-tabs{ role: 'tablist' }
-      %li{ class: active_when(active_tab == 'new'), role: 'presentation' }
-        %a{ href: '#create-new-cluster-pane', id: 'create-new-cluster-tab', data: { toggle: 'tab' }, role: 'tab' }
+    %ul.nav-links.nav-tabs.gitlab-tabs.nav{ role: 'tablist' }
+      %li.nav-item{ role: 'presentation' }
+        %a.nav-link{ href: '#create-new-cluster-pane', id: 'create-new-cluster-tab', class: active_when(active_tab == 'new'), data: { toggle: 'tab' }, role: 'tab' }
           %span Create new Cluster on GKE
-      %li{ class: active_when(active_tab == 'existing'), role: 'presentation' }
-        %a{ href: '#add-existing-cluster-pane', id: 'add-existing-cluster-tab', data: { toggle: 'tab' }, role: 'tab' }
+      %li.nav-item{ role: 'presentation' }
+        %a.nav-link{ href: '#add-existing-cluster-pane', id: 'add-existing-cluster-tab', class: active_when(active_tab == 'existing'), data: { toggle: 'tab' }, role: 'tab' }
           %span Add existing cluster
 
     .tab-content.gitlab-tab-content