FConsoleVariableBase::SetOnChangedCallback behaves incompatibly with previous versions

FConsoleVariable::OnChangedCallback was changed to a multicast delegate in 4.26.
Along with this, FConsoleVariableBase::SetOnChangedCallback was implemented to emulate a single delegate for compatibility, but it actually behaves incompatibly.

The following workaround works

	virtual void SetOnChangedCallback(const FConsoleVariableDelegate& Callback) 
	{
		OnChangedCallback.Remove(LegacyDelegateHandle);
#if 0
		OnChangedCallback.Add(Callback); 
#else
		LegacyDelegateHandle = OnChangedCallback.Add(Callback); 
#endif
	}

1. Call FConsoleVariableBase::SetOnChangedCallback multiple times

Result:

All delegates were registered.

Expected Result:

Only the last delegate was registered.