[rust/all] Remove .iter() on array example (#4230)

As of Rust 1.53.0, arrays implement the IntoIterator trait, making .iter() on an array unnecessary

fr-fr/rust-fr.html.markdown

@@ -221,7 +221,7 @@ fn main() {
 
     // `for` boucles / itération
     let array = [1, 2, 3];
-    for i in array.iter() {
+    for i in array {
         println!("{}", i);
     }