nak: drop unnecessary reference on both sides of ==

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/38807>

src/nouveau/compiler/nak/ssa_value.rs

@@ -308,7 +308,7 @@ fn test_ssa_ref_round_trip() {
             .collect();
 
         let ssa_ref = SSARef::new(&vec);
-        assert!(&ssa_ref[..] == &vec[..]);
+        assert!(ssa_ref[..] == vec[..]);
     }
 }