Revert "[gpos] Break cycle-of-2 when cursive attaching"

This reverts commit 7090707de6.

src/hb-ot-layout-gpos-table.hh

@@ -1692,12 +1692,6 @@ struct CursivePosFormat1
     else
       pos[child].x_offset = x_offset;
 
-    /* If parent was attached to child, break them free.
-     * https://github.com/harfbuzz/harfbuzz/issues/2469
-     */
-    if (unlikely (pos[parent].attach_chain() = -pos[child].attach_chain()))
-      pos[parent].attach_chain() = 0;
-
     buffer->idx++;
     return_trace (true);
   }