Fix nostd test

src/fields/primitive/copy_access/primitive_unit.rs

@@ -94,7 +94,7 @@ mod tests {
                 #[allow(clippy::unit_cmp)]
                 #[test]
                 fn [<test_unit_ $endian endian>]() {
-                    let mut storage = vec![0; 1024];
+                    let mut storage = [0; 1024];
 
                     type Field1 = PrimitiveField<(), $endian_type, 5>;
                     type Field2 = PrimitiveField<(), $endian_type, 123>;
@@ -112,7 +112,7 @@ mod tests {
 
                     // Zero-sized types do not mutate the storage, so it should remain
                     // unchanged for all of time.
-                    assert_eq!(storage, vec![0; 1024]);
+                    assert_eq!(storage, [0; 1024]);
                 }
             }
         };