Change wiki from GitHub Wiki to Scrapbox(Ruby-no-Kai)

Author: snoozer05

_includes/sidebar.html

@@ -17,7 +17,7 @@ <h2 id='id4'>コミュニケーション</h2>
   <li>Twitter <a href='https://twitter.com/rubysapporo'>@rubysapporo</a></li>
   <li>Discord <a href='https:https://ruby-no-kai.org/mailinglist.html'>ruby-no-kai#ruby-sapporo</a></li>
   <li>ハッシュタグ <a href='https://twitter.com/hashtag/rubysapporo?src=hash'>#rubysapporo</a></li>
-  <li><a href='https://github.com/ruby-sapporo/ruby-sapporo.org/wiki'>Wiki</a></li>
+  <li><a href='https://scrapbox.io/ruby-no-kai/Ruby%E6%9C%AD%E5%B9%8C'>Wiki</a></li>
 </ul>
 
 <h2 id='id3'>リンク</h2>