Corrected SQL upgrade format

* Added back the aliases.
Thanks to @Haikenz!

sql-files/upgrades/upgrade_20180830.sql

@@ -1,3 +1,3 @@
-UPDATE `char` SET `char`.`skill_point` = `char`.`skill_point` + `skill`.`lv` WHERE `skill`.`id` = 2049 AND `char`.`char_id` = `skill`.`char_id`;
+UPDATE `char` ch, `skill` sk SET `ch`.`skill_point` = `ch`.`skill_point` + `sk`.`lv` WHERE `sk`.`id` = 2049 AND `ch`.`char_id` = `sk`.`char_id`;
 
 DELETE FROM `skill` WHERE `id` = 2049;