[Bug][sql] fix mysql create sentence bug (#6140)

* fix mysql create sentence bug

Co-authored-by: JinyLeeChina <297062848@qq.com>

sql/dolphinscheduler_mysql.sql

@@ -817,7 +817,7 @@ CREATE TABLE `t_ds_task_instance` (
   `task_instance_priority` int(11) DEFAULT NULL COMMENT 'task instance priority:0 Highest,1 High,2 Medium,3 Low,4 Lowest',
   `worker_group` varchar(64) DEFAULT NULL COMMENT 'worker group id',
   `environment_code` bigint(20) DEFAULT '-1' COMMENT 'environment code',
-  `environment_config` text DEFAULT '' COMMENT 'this config contains many environment variables config',
+  `environment_config` text COMMENT 'this config contains many environment variables config',
   `executor_id` int(11) DEFAULT NULL,
   `first_submit_time` datetime DEFAULT NULL COMMENT 'task first submit time',
   `delay_time` int(4) DEFAULT '0' COMMENT 'task delay execution time',
@@ -989,7 +989,7 @@ CREATE TABLE `t_ds_environment` (
   `update_time` timestamp NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
   PRIMARY KEY (`id`),
   UNIQUE KEY `environment_name_unique` (`name`),
-  UNIQUE KEY `environment_code_unique` (`code`),
+  UNIQUE KEY `environment_code_unique` (`code`)
 ) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;
 
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