Remove redundant DROP TABLE from test case

mysql-test/r/subselect.result

@@ -2196,13 +2196,6 @@ ERROR 42S22: Reference 'xx' not supported (forward reference in item list)
 select 1 = ALL (select 1 from t1 where 1 = xx ), 1 as xx from DUAL;
 ERROR 42S22: Reference 'xx' not supported (forward reference in item list)
 drop table t1;
-drop table if exists t1, t2, t3, t4, t5;
-Warnings:
-Note	1051	Unknown table 't1'
-Note	1051	Unknown table 't2'
-Note	1051	Unknown table 't3'
-Note	1051	Unknown table 't4'
-Note	1051	Unknown table 't5'
 CREATE TABLE t1 (
 categoryId int(11) NOT NULL,
 courseId int(11) NOT NULL,

mysql-test/t/subselect.test

@@ -1467,7 +1467,6 @@ select 1 = ALL (select 1 from t1 where 1 = xx ), 1 as xx from DUAL;
 drop table t1;
 
 # Test for BUG#8218
-drop table if exists t1, t2, t3, t4, t5;
 
 CREATE TABLE t1 (
   categoryId int(11) NOT NULL,