fix(Core/DB): Fix Malygos not engaging due to IMMUNE_TO_PC spawn flag (#25121)

Co-authored-by: blinkysc <blinkysc@users.noreply.github.com>

data/sql/updates/pending_db_world/rev_1773882866738187733.sql

@@ -0,0 +1,2 @@
+-- Remove incorrect IMMUNE_TO_PC from Malygos spawn flags
+UPDATE `creature` SET `unit_flags` = 0 WHERE `guid` = 132313 AND `id1` = 28859;

src/server/game/Entities/Creature/Creature.cpp

@@ -2758,10 +2758,6 @@ void Creature::AtEngage(Unit* target)
 {
     Unit::AtEngage(target);
 
-    // If we somehow engage in combat with a player while immune, remove immunity so they can fight back
-    if (target && IsImmuneToPC() && target->GetCharmerOrOwnerPlayerOrPlayerItself())
-        SetImmuneToPC(false);
-
     if (!IsStandState())
         SetStandState(UNIT_STAND_STATE_STAND);