Fix bug in milestones edit JS, check for due date rather than desc as

WG Chairs can't edit the latter
 - Legacy-Id: 4590

Author: OleLaursen

static/js/edit-milestones.js

@@ -10,7 +10,7 @@ jQuery(function () {
 
     function setSubmitButtonState() {
         var action, label;
-        if (jQuery("#milestones-form input[name$=desc]:visible").length > 0)
+        if (jQuery("#milestones-form input[name$=due]:visible").length > 0)
             action = "review";
         else
             action = "save";