Highlight the currently selected locale instead of hiding it.

I found the current behavior a bit confusing when working on #2960. I
think it's pretty weird to select a locale, and then have it disappear
from the list. Now, we highlight the current locale in blue.

Author: jfly

WcaOnRails/app/views/layouts/_navigation.html.erb

@@ -92,13 +92,11 @@
           </a>
           <ul class="dropdown-menu countries" role="menu">
             <% Locales::AVAILABLE.each do |l, data| %>
-              <% unless l == I18n.locale %>
-                <li>
-                  <%= link_to update_locale_path(l), method: :patch do %>
-                    <%= flag_icon data[:flag_id] %> <%= data[:name] %>
-                  <% end %>
-                </li>
-              <% end %>
+              <li class="<%= l == I18n.locale ? "active" : "" %>">
+                <%= link_to update_locale_path(l), method: :patch do %>
+                  <%= flag_icon data[:flag_id] %> <%= data[:name] %>
+                <% end %>
+              </li>
             <% end %>
           </ul>
         </li>