Core/Misc: Remove unneeded ToCreature() casts

Remove some ToCreature() casts not needed anymore after 1ee90e1022 changes that moved IsPet(), IsTotem(), IsSummon(), IsGuardian(), IsHunterPet() and IsVehicle() from Creature to Unit

src/server/scripts/Spells/spell_pet.cpp

@@ -1367,7 +1367,7 @@ public:
             if (GetCaster()->GetOwner()->ToPlayer())
             {
                 //  Pet's base damage changes depending on happiness
-                if (GetCaster()->IsPet() && GetCaster()->ToPet()->IsHunterPet())
+                if (GetCaster()->IsPet() && GetCaster()->IsHunterPet())
                 {
                     switch (GetCaster()->ToPet()->GetHappinessState())
                     {