Remove link to nonexistent file main.js

Commit 8933085fce11667a8f734987b45193a65a8bbff3 deleted main.js,
but mistakenly removed the link to main.css instead of main.js.
The link to main.css was re-added in d675df7220404a806d029146478d321b7af3e137.

_includes/footer.html

@@ -15,6 +15,5 @@
     <script src="/lib/js/jquery.goup.min.js"></script>
     <script src="/lib/js/bootstrap.min.js"></script>
     <script src="/lib/js/fastclick.min.js"></script>
-    <script src="/assets/js/main.js"></script>
   </body>
 </html>