k12: fix Clippy lint (#656)

Author: newpavlov

k12/tests/mod.rs

@@ -63,7 +63,7 @@ fn pat_c() {
         hex!("75d2f86a2e644566726b4fbcfc5657b9dbcf070c7b0dca06450ab291d7443bcf"),
     ];
     for i in 0..4 {
-        let m: Vec<u8> = iter::repeat(0xFF).take(2usize.pow(i) - 1).collect();
+        let m: Vec<u8> = iter::repeat_n(0xFF, 2usize.pow(i) - 1).collect();
         let len = 41usize.pow(i);
         let c: Vec<u8> = (0..len).map(|j| (j % 251) as u8).collect();
         let mut h = KangarooTwelve::from_core(KangarooTwelveCore::new(&c));