AI/SmartAI: Remove a silly incorrect piece of code that was breaking react state swaps on SAI creatures. Fixes #21353.

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

@@ -545,11 +545,6 @@ void SmartAI::MoveInLineOfSight(Unit* who)
     CreatureAI::MoveInLineOfSight(who);
 }
 
-bool SmartAI::CanAIAttack(Unit const* /*who*/) const
-{
-    return !(me->HasReactState(REACT_PASSIVE));
-}
-
 bool SmartAI::AssistPlayerInCombatAgainst(Unit* who)
 {
     if (me->HasReactState(REACT_PASSIVE) || !IsAIControlled())

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

@@ -145,9 +145,6 @@ class TC_GAME_API SmartAI : public CreatureAI
         // Called when creature gets charmed by another unit
         void OnCharmed(bool apply) override;
 
-        // Called when victim is in line of sight
-        bool CanAIAttack(Unit const* who) const override;
-
         // Used in scripts to share variables
         void DoAction(int32 param = 0) override;