Remove extra specificity

Author: wylieconlon

x-pack/plugins/lens/public/drag_drop/_drag_drop.scss

@@ -1,3 +1,7 @@
+.lnsDragDrop-isNotDroppable {
+  opacity: .5;
+}
+
 // Fix specificity by chaining classes
 
 .lnsDragDrop.lnsDragDrop-isDropTarget {
@@ -7,7 +11,3 @@
 .lnsDragDrop.lnsDragDrop-isActiveDropTarget {
   background-color: transparentize($euiColorSecondary, .75);
 }
-
-.lnsDragDrop.lnsDragDrop-isNotDroppable {
-  opacity: .5;
-}