additional fix for bug #13372 (decimal union)

mysql-test/r/union.result:
  test result changed

mysql-test/r/union.result

@@ -565,7 +565,7 @@ a
 show create table t1;
 Table	Create Table
 t1	CREATE TABLE `t1` (
-  `a` double(53,1) NOT NULL default '0.0'
+  `a` double(21,1) NOT NULL default '0.0'
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 drop table t1;
 create table t2 (it1 tinyint, it2 tinyint not null, i int not null, ib bigint, f float, d double, y year, da date, dt datetime, sc char(10), sv varchar(10), b blob, tx text);