Adjusted the results of pbxt.subselect after the latest merge 5.1->5.2->5.3.

mysql-test/suite/pbxt/r/subselect.result

@@ -1267,7 +1267,7 @@ insert into t1 values (1,0), (2,0), (3,0);
 insert into t2 values (1,1), (2,1), (3,1), (2,2);
 update ignore t1 set b=(select b from t2 where t1.a=t2.a);
 Warnings:
-Error	1242	Subquery returns more than 1 row
+Warning	1242	Subquery returns more than 1 row
 select * from t1;
 a	b
 1	1