Core/Threat: Threat system adjustments

Port From (https://github.com/TrinityCore/TrinityCore/commit/392a644dc8562ea54b9c185a2776fceb1006e2cd)

Source/Game/Entities/Unit/Unit.Combat.cs

@@ -152,8 +152,6 @@ namespace Game.Entities
 
         public bool CanHaveThreatList() { return m_threatManager.CanHaveThreatList(); }
 
-        void SendThreatListUpdate() { m_threatManager.SendThreatListToClients(); }
-
         // For NPCs with threat list: Whether there are any enemies on our threat list
         // For other units: Whether we're in combat
         // This value is different from IsInCombat when a projectile spell is midair (combat on launch - threat+aggro on impact)