fix(DB/Spells): define Dust Field as a positive spell (#7798)

- Closes #5392
- Closes #6285

data/sql/updates/pending_db_world/rev_1631201007246764700.sql

@@ -0,0 +1,5 @@
+INSERT INTO `version_db_world` (`sql_rev`) VALUES ('1631201007246764700');
+
+DELETE FROM `spell_custom_attr` WHERE `spell_id`=21909;
+INSERT INTO `spell_custom_attr` VALUES
+(21909,0x06000000);