[Warlock] GFG Demonic Power bug (#9869)

* Update sc_warlock_pets.cpp

This behavior still exists as of PTR 11.1 
so i am attempting to apply it for simc SimCMinMax/WoW-BugTracker#1302

* Bug handling flag

---------

Co-authored-by: Azevara <46403881+Azevara@users.noreply.github.com>

engine/class_modules/warlock/sc_warlock_pets.cpp

@@ -576,6 +576,16 @@ struct legion_strike_t : public warlock_pet_melee_attack_t
 
     return m;
   }
+
+  double cost_pct_multiplier() const override
+  {
+    double c = warlock_pet_melee_attack_t::cost_pct_multiplier();
+
+    if ( !main_pet && p()->buffs.demonic_power->check() && p()->bugs )
+      c *= 1.0 + p()->o()->talents.demonic_power_buff->effectN( 4 ).percent();
+
+    return c;
+  }
 };
 
 struct immutable_hatred_t : public warlock_pet_melee_attack_t