Remove first line of schema file causing issues for older MySQL clients (librenms#18278)

* Clean up MySQL schema file

Removing this line which is causing issues for some people installing for now.

* Remove sandbox mode comment from MySQL schema

Author: laf

database/schema/mysql-schema.sql

@@ -1,4 +1,3 @@
-/*M!999999\- enable the sandbox mode */ 
 /*!40103 SET @OLD_TIME_ZONE=@@TIME_ZONE */;
 /*!40103 SET TIME_ZONE='+00:00' */;
 /*!40014 SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0 */;
@@ -3010,7 +3009,6 @@ CREATE TABLE `wireless_sensors` (
 /*!40014 SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS */;
 /*!40111 SET SQL_NOTES=@OLD_SQL_NOTES */;
 
-/*M!999999\- enable the sandbox mode */ 
 INSERT INTO `migrations` (`id`, `migration`, `batch`) VALUES (1,'2018_07_03_091314_create_access_points_table',1);
 INSERT INTO `migrations` (`id`, `migration`, `batch`) VALUES (2,'2018_07_03_091314_create_alert_device_map_table',1);
 INSERT INTO `migrations` (`id`, `migration`, `batch`) VALUES (3,'2018_07_03_091314_create_alert_group_map_table',1);