Ignore dead code lint in test

    warning: fields `x` and `y` are never read
       --> tests/test_ensure.rs:467:13
        |
    466 |     pub struct Point {
        |                ----- fields in this struct
    467 |         pub x: i32,
        |             ^
    468 |         pub y: i32,
        |             ^
        |
        = note: `Point` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis
        = note: `#[warn(dead_code)]` on by default

tests/test_ensure.rs

@@ -464,7 +464,9 @@ fn test_trailer() {
 fn test_whitespace() {
     #[derive(Debug)]
     pub struct Point {
+        #[allow(dead_code)]
         pub x: i32,
+        #[allow(dead_code)]
         pub y: i32,
     }