fix warning by using iter() instead of into_iter()

Change into_iter() to iter() in impl_zip_iter macro to avoid
the compliation warning related to the potentially upcoming
incompatibility with array.into_iter()
rust-lang/rust#66145.

src/ziptuple.rs

@@ -39,9 +39,8 @@ pub struct Zip<T> {
 /// assert_eq!(results, [0 + 3, 10 + 7, 29, 36]);
 /// ```
 pub fn multizip<T, U>(t: U) -> Zip<T>
-where
-    Zip<T>: From<U>,
-    Zip<T>: Iterator,
+    where Zip<T>: From<U>,
+          Zip<T>: Iterator,
 {
     Zip::from(t)
 }