Core/Spells: Removed SpellEffIndex effIndex argument from spell effect handlers, it was commented out in almost every handler

Port From (https://github.com/TrinityCore/TrinityCore/commit/3dd75a49b190098010803014072c0c8bee2996bd)

Source/Game/Spells/SpellManager.cs

@@ -4017,7 +4017,7 @@ namespace Game.Entities
 
         public delegate void AuraEffectHandler(AuraEffect effect, AuraApplication aurApp, AuraEffectHandleModes mode, bool apply);
         Dictionary<AuraType, AuraEffectHandler> AuraEffectHandlers = new();
-        public delegate void SpellEffectHandler(Spell spell, uint effectIndex);
+        public delegate void SpellEffectHandler(Spell spell);
         Dictionary<SpellEffectName, SpellEffectHandler> SpellEffectsHandlers = new();
 
         public MultiMap<uint, uint> PetFamilySpellsStorage = new();