remove unneeded code.

remove unneeded code.

diff --git a/plugin.rb b/plugin.rb
index 871ca6a..a95fafe 100644
--- a/plugin.rb
+++ b/plugin.rb
@@ -7,8 +7,6 @@
 # url: https://github.com/techAPJ/discourse-prioritize-generic-onebox
 
 class Onebox::Engine::WhitelistedGenericOnebox
-  include Onebox::Engine
-
   def placeholder_html
     return article_html if is_article?
     return image_html if is_image?

GitHub sha: 0cf54afc698d3498a1d4f7ee123934c9667882c5