Core/Movement: Use SetLevitate(true/false) instead of AddUnit/RemoveUnit.

src/server/game/AI/SmartScripts/SmartAI.cpp

@@ -731,12 +731,12 @@ void SmartAI::SetFly(bool fly)
 {
     if (fly)
     {
-        me->AddUnitMovementFlag(MOVEMENTFLAG_LEVITATING);
+        me->SetLevitate(true);
         me->SetByteFlag(UNIT_FIELD_BYTES_1, 3, 0x01);
     }
     else
     {
-        me->RemoveUnitMovementFlag(MOVEMENTFLAG_LEVITATING);
+        me->SetLevitate(false);
         me->RemoveByteFlag(UNIT_FIELD_BYTES_1, 3, 0x01);
     }
     me->SetFlying(fly);