Remove serde derive references (#4830)

* remove remaining uses of serde_derive

* fix lockfile

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Co-authored-by: João Oliveira <hello@jxs.pt>

common/account_utils/src/validator_definitions.rs

@@ -9,7 +9,7 @@ use crate::{
 use directory::ensure_dir_exists;
 use eth2_keystore::Keystore;
 use regex::Regex;
-use serde_derive::{Deserialize, Serialize};
+use serde::{Deserialize, Serialize};
 use slog::{error, Logger};
 use std::collections::HashSet;
 use std::fs::{self, File};