chore: remove an unneeded xmlSetNs-after-reparent call

The function `reparent_node_with` is already doing the right thing.

ext/nokogiri/xml_node.c

@@ -69,11 +69,6 @@ relink_namespace(xmlNodePtr reparented)
   /* Avoid segv when relinking against unlinked nodes. */
   if (reparented->type != XML_ELEMENT_NODE || !reparented->parent) { return; }
 
-  /* Make sure that our reparented node has the correct namespaces */
-  if (!reparented->ns && reparented->doc != (xmlDocPtr)reparented->parent) {
-    xmlSetNs(reparented, reparented->parent->ns);
-  }
-
   /* Search our parents for an existing definition */
   if (reparented->nsDef) {
     xmlNsPtr curr = reparented->nsDef;