Revert "Updated perfect-scrollbar to 0.6.10"

This reverts commit bc5f82f624.

web/templates/head.html

@@ -54,7 +54,7 @@
     <script src="/static/js/bootstrap-colorpicker.min.js"></script>
     <script src="/static/js/react-bootstrap-0.28.1.js"></script>
     <script src="/static/js/velocity.min.js"></script>
-    <script src="/static/js/perfect-scrollbar-0.6.10.jquery.min.js"></script>
+    <script src="/static/js/perfect-scrollbar-0.6.7.jquery.min.js"></script>
     <script src="/static/js/jquery-dragster/jquery.dragster.js"></script>
     <script src="/static/js/babel-polyfill-6.1.18.min.js"></script>
     <script src="/static/js/katex.min.js"></script>