Remove duplicate new cluster button

Changelog: fixed

app/views/clusters/clusters/_cluster_list.html.haml

-- if !clusters.empty?
-  .top-area.adjust
-    .gl-display-block.gl-text-right.gl-my-4.gl-w-full
-      - if clusterable.can_add_cluster?
-        = link_to s_('ClusterIntegration|Connect cluster with certificate'), clusterable.new_path, class: 'btn gl-button btn-confirm js-add-cluster gl-py-2', data: { qa_selector: 'integrate_kubernetes_cluster_button' }
-      - else
-        %span.btn.gl-button.btn-confirm.js-add-cluster.disabled.gl-py-2
-          = s_("ClusterIntegration|Connect cluster with certificate")
-
-.js-clusters-main-view{ data: js_clusters_list_data(clusterable) }

app/views/clusters/clusters/index.html.haml

@@ -9,4 +9,4 @@
       .js-clusters-main-view{ data: js_clusters_data(clusterable) }
 
   - else
-    = render 'cluster_list', clusters: @clusters
+    .js-clusters-main-view{ data: js_clusters_list_data(clusterable) }

locale/gitlab.pot

@@ -8071,9 +8071,6 @@ msgstr ""
 msgid "ClusterIntegration|Clusters are utilized by selecting the nearest ancestor with a matching environment scope. For example, project clusters will override group clusters. %{linkStart}More information%{linkEnd}"
 msgstr ""
 
-msgid "ClusterIntegration|Connect cluster with certificate"
-msgstr ""
-
 msgid "ClusterIntegration|Connect existing cluster"
 msgstr ""