Add missing pstrdup

Lifetime of the input string is not right, so create a separate copy.

Author: Amit Langote
Discussion: https://postgr.es/m/a2773420-50d1-0a42-3396-fe42b0921134@lab.ntt.co.jp

src/backend/commands/tablecmds.c

@@ -14568,7 +14568,8 @@ CloneRowTriggersToPartition(Relation parent, Relation partition)
 
 				col = TupleDescAttr(parent->rd_att,
 									trigForm->tgattr.values[i] - 1);
-				cols = lappend(cols, makeString(NameStr(col->attname)));
+				cols = lappend(cols,
+							   makeString(pstrdup(NameStr(col->attname))));
 			}
 		}