Fix Rust beta compiler errors 1.78.0-beta.1 (#5439)

* remove redundant imports

* fix test

* contains key

* fmt

* Merge branch 'unstable' into fix-beta-compiler

crypto/eth2_keystore/src/keystore.rs

@@ -23,7 +23,6 @@ use serde::{Deserialize, Serialize};
 use sha2::{Digest, Sha256};
 use std::fs::File;
 use std::io::{Read, Write};
-use std::iter::FromIterator;
 use std::path::Path;
 use std::str;
 use unicode_normalization::UnicodeNormalization;