Update enabled Kubernetes cluster button to "Kubernetes configured"

See
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/16900#note_60175507

app/presenters/project_presenter.rb

@@ -271,7 +271,7 @@ class ProjectPresenter < Gitlab::View::Presenter::Delegated
       end
 
       OpenStruct.new(enabled: !clusters.empty?,
-                     label: clusters.empty? ? _('Add Kubernetes cluster') : n_('Kubernetes cluster', 'Kubernetes clusters', clusters.size),
+                     label: clusters.empty? ? _('Add Kubernetes cluster') : _('Kubernetes configured'),
                      link: cluster_link)
     end
   end

spec/features/projects/show_project_spec.rb

@@ -111,7 +111,7 @@ describe 'Project show page', :feature do
             visit project_path(project)
 
             page.within('.project-stats') do
-              expect(page).to have_link('Kubernetes cluster', href: project_cluster_path(project, cluster))
+              expect(page).to have_link('Kubernetes configured', href: project_cluster_path(project, cluster))
             end
           end
         end
@@ -149,7 +149,7 @@ describe 'Project show page', :feature do
         it 'no Kubernetes cluster button if can not manage clusters' do
           page.within('.project-stats') do
             expect(page).not_to have_link('Add Kubernetes cluster')
-            expect(page).not_to have_link('Kubernetes cluster')
+            expect(page).not_to have_link('Kubernetes configured')
           end
         end
       end
@@ -292,7 +292,7 @@ describe 'Project show page', :feature do
             visit project_path(project)
 
             page.within('.project-stats') do
-              expect(page).to have_link('Kubernetes cluster', href: project_cluster_path(project, cluster))
+              expect(page).to have_link('Kubernetes configured', href: project_cluster_path(project, cluster))
             end
           end
         end

spec/presenters/project_presenter_spec.rb

@@ -333,7 +333,7 @@ describe ProjectPresenter do
           cluster = create(:cluster, projects: [project])
 
           expect(presenter.kubernetes_cluster_anchor_data).to eq(OpenStruct.new(enabled: true,
-                                                                                label: 'Kubernetes cluster',
+                                                                                label: 'Kubernetes configured',
                                                                                 link: presenter.project_cluster_path(project, cluster)))
         end
 
@@ -343,7 +343,7 @@ describe ProjectPresenter do
           create(:cluster, projects: [project])
 
           expect(presenter.kubernetes_cluster_anchor_data).to eq(OpenStruct.new(enabled: true,
-                                                                                label: 'Kubernetes clusters',
+                                                                                label: 'Kubernetes configured',
                                                                                 link: presenter.project_clusters_path(project)))
         end