DB/Spells: added missing scriptname to Druid's bear form Vengeance proc

sql/updates/world/4.3.4/2020_07_26_00_world.sql

@@ -0,0 +1,3 @@
+DELETE FROM `spell_script_names` WHERE `spell_id`= 84840;
+INSERT INTO `spell_script_names` (`spell_id`, `ScriptName`) VALUES
+(84840, 'spell_gen_vengeance');