Clean up and unify exercises

exercises/05_vecs/vecs1.rs

@@ -1,11 +1,7 @@
-// vecs1.rs
-//
 // Your task is to create a `Vec` which holds the exact same elements as in the
 // array `a`.
 //
 // Make me compile and pass the test!
-//
-// Execute `rustlings hint vecs1` or use the `hint` watch subcommand for a hint.
 
 fn array_and_vec() -> ([i32; 4], Vec<i32>) {
     let a = [10, 20, 30, 40]; // a plain array

exercises/05_vecs/vecs2.rs

@@ -1,11 +1,7 @@
-// vecs2.rs
-//
 // A Vec of even numbers is given. Your task is to complete the loop so that
 // each number in the Vec is multiplied by 2.
 //
 // Make me pass the test!
-//
-// Execute `rustlings hint vecs2` or use the `hint` watch subcommand for a hint.
 
 fn vec_loop(mut v: Vec<i32>) -> Vec<i32> {
     for element in v.iter_mut() {