Reducing current in a circuit without reducing voltage
This question pops-up regularly in different forms.

The specification mean that the supply can provide up to 8 Amps. It does not mean that it will deliver 8 Amps. 

Compare it to when you say "I can lift 40 kilos".
So what if you have to lift 10 Kilos? Do you take something like sleeping pills to reduce your strength? No, you lift the 10 kilo and have power to spare.

So a supply which can deliver up to 8 amps can easily also deliver 2.1 Amps and have some spare.