Update code highlighting theme from Base16::Monokai to just Monokai

Author: lord

source/layouts/layout.erb

@@ -23,7 +23,7 @@ under the License.
     <title><%= current_page.data.title || "API Documentation" %></title>
 
     <style>
-      <%= Rouge::Themes::Base16::Monokai.render(:scope => '.highlight') %>
+      <%= Rouge::Themes::Monokai.render(:scope => '.highlight') %>
     </style>
     <%= stylesheet_link_tag :screen, media: :screen %>
     <%= stylesheet_link_tag :print, media: :print %>