Fix code blocks in Markdown not knowing about the user's color scheme

lib/redcarpet/render/gitlab_html.rb

@@ -12,10 +12,12 @@ class Redcarpet::Render::GitlabHTML < Redcarpet::Render::HTML
   def block_code(code, language)
     options = { options: {encoding: 'utf-8'} }
 
+    h.content_tag :div, class: h.user_color_scheme_class do
       if Pygments::Lexer.find(language)
         Pygments.highlight(code, options.merge(lexer: language.downcase))
       else
         Pygments.highlight(code, options)
+      end.html_safe
     end
   end