rtiow: fix unused-imports build errors.

rtiow/noise_explorer_warp/src/main.rs

@@ -1,5 +1,3 @@
-use warp;
-
 fn main() {
     println!("Hello, world!");
 }

rtiow/renderer/src/scenes/spheramid.rs

@@ -1,20 +1,17 @@
 use crate::camera::Camera;
 use crate::hitable::Hit;
 use crate::hitable_list::HitableList;
-use crate::kdtree::KDTree;
 use crate::material::Dielectric;
 use crate::material::Lambertian;
 use crate::material::Metal;
 use crate::moving_sphere::MovingSphere;
 use crate::rect::XYRect;
-use crate::rect::XZRect;
 use crate::renderer::Opt;
 use crate::renderer::Scene;
 use crate::sphere::Sphere;
 use crate::texture::CheckerTexture;
 use crate::texture::ConstantTexture;
 use crate::texture::EnvMap;
-use crate::texture::Texture;
 use crate::vec3::Vec3;
 
 // Draws many spheres along each positive axis.