Remove redundant duplication

Author: Vladyslav Tymofeiev

lms/templates/main.html

@@ -215,7 +215,6 @@
   <script type="text/javascript" src="${static.url('js/header/header.js')}"></script>
   <%static:optional_include_mako file="body-extra.html" is_theming_enabled="True" />
   <script type="text/javascript" src="${static.url('js/src/jquery_extend_patch.js')}"></script>
-  <script type="text/javascript" src="${static.url('js/src/jquery_extend_patch.js')}"></script>
 </body>
 </html>