Merge pull request #13735 from skhilko/master

Fix bug where a panel recieve extra top border when placed within a collapsible panel

less/panels.less

@@ -206,7 +206,7 @@
 
   .panel-heading {
     border-bottom: 0;
-    + .panel-collapse .panel-body {
+    + .panel-collapse > .panel-body {
       border-top: 1px solid @panel-inner-border;
     }
   }