Use adequate icon for Forks link on sidebar. #2406

app/views/layouts/nav/_project.html.haml

@@ -101,7 +101,7 @@
   - if project_nav_tab? :forks
     = nav_link(controller: :forks, action: :index) do
       = link_to namespace_project_forks_path(@project.namespace, @project), title: 'Forks', class: 'shortcuts-wiki' do
-        = icon('book fw')
+        = icon('code-fork fw')
         %span
           Forks