No, a small series resistor.
Note I said 2.2Ω above, and the schematic shows 2.7Ω, it doesn't matter, you need to choose to suit the current. How do you choose? Good question! I was aiming for a small voltage drop at the LED current of about 150mA per string. I guess you need to aim for a voltage drop of more than the expected change in Vf from possible heating, but I cannot give you an equation, this is part of the art of electronics.