Revert "Fixed app menu openning animation lag (#523)"

This reverts commit e2dc72c.

Author: clefebvre

src/Mint-Y/cinnamon/sass/_common.scss

@@ -275,6 +275,7 @@ StScrollBar {
 .menu {
   color: $fg_color;
   background-color: $bg_color;
+  box-shadow: 0 0 6px $shadow_color;
 
   &-top {
     border-radius: 0 0 $radius $radius;