improve code after review

app/views/projects/builds/_sidebar.html.haml

@@ -90,7 +90,7 @@
 
         - if @build.trigger_request.variables
           %p
-            .btn.group.btn-group-justified.reveal-variables Reveal Variables
+            %button.btn.group.btn-group-justified.reveal-variables Reveal Variables
 
 
           - @build.trigger_request.variables.each do |key, value|

spec/features/projects/builds_spec.rb

@@ -177,7 +177,7 @@ describe "Builds" do
         expect(page).not_to have_css('.js-build-variable')
         expect(page).not_to have_css('.js-build-value')
      
-        find('.reveal-variables').click
+        click_button 'Reveal Variables'
 
         expect(page).not_to have_css('.reveal-variables')
         expect(page).to have_selector('.js-build-variable', text: 'TRIGGER_KEY_1')