fix(test): par_azip9 — drop approx-gated itertools helpers (CI rayon-only)

`tests/par_azip.rs` has `use itertools::{assert_equal, cloned, enumerate}`
under `#[cfg(feature = "approx")]`, but `test_par_azip9` called
`assert_equal(cloned(&a), x)` at line 85 unconditionally. With approx OFF
the import is excluded and compile fails with E0425.

Latent for as long as the file existed (since PR #73 era); never surfaced
because no CI matrix combination ran `--features rayon` without approx.
W-I4's new `hpc-stream-parallel` job exercises exactly that combination
and tripped the failure.

Fix: replace `assert_equal(cloned(&a), x)` with `assert_eq!(a, x)` —
both `a` and `x` are `Array<i32, _>` and the file's other tests already
use direct `assert_eq!`. Trim the now-dead `assert_equal, cloned` from
the still-needed (test_par_azip3) `enumerate` import.

Verified clean compile + 6/6 tests pass under both:
  cargo test --features rayon --test par_azip
  cargo test --features "rayon approx" --test par_azip

https://claude.ai/code/session_01UwJuKqP828qyX1VkLgGJFS

Author: claude

tests/par_azip.rs

@@ -1,7 +1,7 @@
 #![cfg(feature = "rayon")]
 
 #[cfg(feature = "approx")]
-use itertools::{assert_equal, cloned, enumerate};
+use itertools::enumerate;
 use ndarray::parallel::prelude::*;
 use ndarray::prelude::*;
 use std::sync::atomic::{AtomicUsize, Ordering};
@@ -82,5 +82,5 @@ fn test_par_azip9() {
         *a = b + c + d + e + f + g + h + i;
     });
     let x = Array::from_shape_fn(a.dim(), |j| (j * 255) as i32);
-    assert_equal(cloned(&a), x);
+    assert_eq!(a, x);
 }