Resolve stylelint violations in milestones.scss

ee/app/assets/javascripts/burndown_chart/index.js

@@ -32,9 +32,9 @@ export default () => {
       if (currentView !== show) {
         currentView = show;
         $this
-          .addClass('active')
+          .removeClass('btn-inverted')
           .siblings()
-          .removeClass('active');
+          .addClass('btn-inverted');
         switch (show) {
           case 'count':
             chart.setData(openIssuesCount, { label: 'Open issues', animate: true });

ee/app/assets/stylesheets/pages/milestone.scss

@@ -59,18 +59,6 @@
     margin-left: 20px;
     margin-bottom: 2px;
   }
-
-  .btn {
-    @include btn-outline($white-light, $blue-500, $blue-500, $blue-500, $white-light, $blue-600, $blue-600, $blue-700);
-
-    font-size: 12px;
-
-    &.active {
-      background-color: $blue-500;
-      border-color: $blue-600;
-      color: $white-light;
-    }
-  }
 }
 
 .burndown-chart {

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

@@ -9,9 +9,9 @@
     %h3
       Burndown chart
       .btn-group.js-burndown-data-selector
-        %button.btn.btn-sm.active{ data: { show: 'count' } }
+        %button.btn.btn-sm.btn-primary{ data: { show: 'count' } }
           Issues
-        %button.btn.btn-sm{ data: { show: 'weight' } }
+        %button.btn.btn-sm.btn-primary.btn-inverted{ data: { show: 'weight' } }
           Issue weight
   .burndown-chart{ data: { start_date: burndown.start_date.strftime("%Y-%m-%d"), due_date: burndown.due_date.strftime("%Y-%m-%d"), chart_data: burndown.to_json } }