fix timeline arrows (#2069)

app/views/admin/communication/blocks/templates/timeline/_show.html.erb

@@ -38,7 +38,7 @@
             <% end %>
           </ol>
           <% if !block.template.elements.one? %>
-            <div class="timeline-arrows">
+            <div class="actions-arrows">
               <button class="previous" disabled></button>
               <button class="next"></button>
             </div>