add a proper cleanup to innodb.innodb-mdev7046 test

mysql-test/suite/innodb/t/innodb-mdev7046.test

@@ -29,3 +29,6 @@ CREATE TABLE t1(id INT,purchased DATE)PARTITION BY RANGE(YEAR(purchased)) SUBPAR
 ALTER TABLE t1 ENGINE=InnoDB;
 
 drop table t1;
+
+let $datadir=`select @@datadir`;
+--remove_file $datadir/test/db.opt