kernel/object: Remove unused handle type entry

The AddressArbiter type isn't actually used, given the arbiter itself
isn't a direct kernel object (or object that implements the wait object
facilities).

Given this, we can remove the enum entry entirely.

src/core/hle/kernel/object.cpp

@@ -24,7 +24,6 @@ bool Object::IsWaitable() const {
     case HandleType::WritableEvent:
     case HandleType::SharedMemory:
     case HandleType::TransferMemory:
-    case HandleType::AddressArbiter:
     case HandleType::ResourceLimit:
     case HandleType::ClientPort:
     case HandleType::ClientSession: