fix bugs

migrations/mysql/02116_user_algo.sql

@@ -1,4 +1,3 @@
--- migrate:up
 -- 添加 algo 列（如果不存在）
 SET @dbname = DATABASE();
 SET @tablename = 'user';
@@ -35,8 +34,3 @@ PREPARE stmt FROM @sql;
 EXECUTE stmt;
 DEALLOCATE PREPARE stmt;
 
--- migrate:down
-ALTER TABLE `user`
-DROP COLUMN `algo`,
-    DROP COLUMN `salt`;
-