fix end date not matching due date

app/assets/javascripts/burndown_chart/index.js

@@ -15,7 +15,7 @@ $(() => {
 
   if (chartElm.length) {
     const startDate = chartElm.data('startDate');
-    const dueDate = chartElm.data('endDate');
+    const dueDate = chartElm.data('dueDate');
     const chartData = chartElm.data('chartData');
     const openIssuesCount = chartData.map(d => [d[0], d[1]]);
     const openIssuesWeight = chartData.map(d => [d[0], d[2]]);

app/views/shared/milestones/_burndown.html.haml

@@ -31,4 +31,4 @@
           Issues
         %button.btn.btn-xs{ data: { show: 'weight' } }
           Issue Weight
-  .burndown-chart{ data: { start_date: burndown.start_date.strftime("%Y-%m-%d"), end_date: burndown.end_date.strftime("%Y-%m-%d"), chart_data: burndown.chart_data.to_json } }
+  .burndown-chart{ data: { start_date: milestone.start_date.strftime("%Y-%m-%d"), due_date: milestone.due_date.strftime("%Y-%m-%d"), chart_data: burndown.chart_data.to_json } }