rtchallenge: Address cargo clippy.

rtchallenge/examples/glass.rs

@@ -8,7 +8,7 @@ use rtchallenge::prelude::*;
 use rtchallenge::{
     camera::RenderStrategy,
     float::consts::PI,
-    patterns::{test_pattern, BLACK_PAT, WHITE_PAT},
+    patterns::{BLACK_PAT, WHITE_PAT},
     WHITE,
 };