fix(DB/loot): Remove Mana Agate drop from Vultros (#6273)

- Removed Conjured Mana Agate from the drop table because it is a conjured mage item
- Closes https://github.com/azerothcore/azerothcore-wotlk/issues/6249
- Closes https://github.com/chromiecraft/chromiecraft/issues/791

data/sql/updates/pending_db_world/rev_1623193677054313100.sql

@@ -0,0 +1,4 @@
+INSERT INTO `version_db_world` (`sql_rev`) VALUES ('1623193677054313100');
+
+-- Remove Conjured Mana Agate drop from Vultros
+DELETE FROM `creature_loot_template` WHERE `entry` = 462 AND `item` = 5514;