merge order_id migration into the table create sql

migrations/mysql/20200721225616_trades.sql

@@ -4,6 +4,7 @@ CREATE TABLE `trades`
     `gid`            BIGINT UNSIGNED         NOT NULL AUTO_INCREMENT,
 
     `id`             BIGINT UNSIGNED,
+    `order_id`       BIGINT UNSIGNED         NOT NULL,
     `exchange`       VARCHAR(24)             NOT NULL DEFAULT '',
     `symbol`         VARCHAR(8)              NOT NULL,
     `price`          DECIMAL(16, 8) UNSIGNED NOT NULL,

migrations/mysql/20201103173342_trades_add_order_id.sql

@@ -1,7 +1,5 @@
 -- +up
-ALTER TABLE `trades`
-    ADD COLUMN `order_id` BIGINT UNSIGNED NOT NULL;
+SELECT 1;
 
 -- +down
-ALTER TABLE `trades`
-    DROP COLUMN `order_id`;
+SELECT 1;