appDisplay: Return false in acceptDrop when not accepting the drop

Fix what is probably a copy-paste error and return false instead of a
CONTINUE DragMotionResult which is only meant for dragMotion events, not
drop events. This makes sure we don't create a folder when dropping an
app over the drag leeways of another icon.

https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1389

js/ui/appDisplay.js

@@ -1541,7 +1541,7 @@ class AppViewItem extends St.Button {
             return false;
 
         if (this._withinLeeways(x))
-            return DND.DragMotionResult.CONTINUE;
+            return false;
 
         return true;
     }