What's all the fuss? Lamp-holders have always been made for two-wire connection. You've only to look at your standard ceiling pendant. It's comparatively recently that e.g. bare brass lamp-holders, (of the type you get on some older standard lamps), now have to have an added earth connection by way of a little screw on the side. Should the lamp itself be made of metal, an earth connection will be found within the body of the lamp. Where such a lamp requires the bulb-holder to be earthed, (i.e. it's bare metal), it's done through metal to metal contact back to the lamp's earth connection .
If your lamp comes with only two wires, it's designed to be used with only two wires. Go ahead and fit the plug.