Depends on your replationship with your dealer. I lowered mine when it was just a few weeks old - no hassle from the dealer at all. Obviously if one of your new springs breaks, or if a shock absorber goes, you cant expect Renault to help, but everything else should still be covered.
If you ask them to confirm this in writing they probably wont! But there are heavily modified cars (stripped-out, chip, exhaust, brakes etc) on here which Renault still do warranty jobs on.
Welcome to Cliosport by the way!