Fix ui issue for Help#api

app/views/help/_api_layout.html.haml

 .row
   .span3
-    = link_to help_path, class: 'btn append-bottom-20 btn-small' do
-      %i.icon-angle-left
-      Back to help
-    %br
+    .append-bottom-20
+      = link_to help_path, class: 'btn btn-small' do
+        %i.icon-angle-left
+        Back to help
     %ul.nav.nav-pills.nav-stacked
       - %w(README projects project_snippets repositories deploy_keys users groups session issues milestones merge_requests notes system_hooks).each do |file|
         %li{class: file == @category ? 'active' : nil}