This is pretty simple. I replaced all my files with the kamino sky and it had no terrain. So i looked in the sky file. here is the code
Softness(1);
SoftnessParam(60);
TerrainEnable(0);
As you can see TerrainEnable(0) is = to 0 which means its off.
if u want your map to have it on . change the (0) to 1
if you want it off. change to TerrainEnable(0)