Allow stacking flash messages

Author: nlhkabu

warehouse/static/sass/blocks/_notification-bar.scss

@@ -34,7 +34,6 @@
 
 .notification-bar {
   border-bottom: 2px solid $white;
-  border-top: 2px solid $white;
   text-align: center;
   background-color: darken($brand-color, 10);
   color: $white;
@@ -63,10 +62,3 @@
     background-color: $success-color;
   }
 }
-
-// Remove top border when notification-bars are stacked on top of each other,
-// or when notification bar is under a sticky element
-.notification-bar + .notification-bar,
-body.with-sticky > .notification-bar {
-  border-top: 0;
-}