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>

validator_client/src/config.rs

@@ -8,7 +8,7 @@ use directory::{
 };
 use eth2::types::Graffiti;
 use sensitive_url::SensitiveUrl;
-use serde_derive::{Deserialize, Serialize};
+use serde::{Deserialize, Serialize};
 use slog::{info, warn, Logger};
 use std::fs;
 use std::net::IpAddr;