Core/Pets: Fixed pet power regeneration

Closes #12292

src/server/scripts/Northrend/Ulduar/Ulduar/boss_algalon_the_observer.cpp

@@ -334,7 +334,7 @@ class boss_algalon_the_observer : public CreatureScript
                 {
                     case ACTION_START_INTRO:
                     {
-                        me->SetFlag(UNIT_FIELD_FLAGS_2, 0x20);
+                        me->SetFlag(UNIT_FIELD_FLAGS_2, UNIT_FLAG2_INSTANTLY_APPEAR_MODEL);
                         me->SetDisableGravity(true);
                         DoCast(me, SPELL_ARRIVAL, true);
                         DoCast(me, SPELL_RIDE_THE_LIGHTNING, true);