roundedbox: Fix copy-paste error

y coordinates don't care about the right value, they want bottom.

gtk/gtkroundedbox.c

@@ -171,7 +171,7 @@ _gtk_rounded_box_grow (GtkRoundedBox *box,
       box->box.width += left + right;
     }
 
-  if (box->box.height + bottom + right < 0)
+  if (box->box.height + bottom + top < 0)
     {
       box->box.y -= top * box->box.height / (top + bottom);
       box->box.height = 0;