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>

testing/ef_tests/src/cases/genesis_validity.rs

@@ -1,6 +1,6 @@
 use super::*;
 use crate::decode::{ssz_decode_state, yaml_decode_file};
-use serde_derive::Deserialize;
+use serde::Deserialize;
 use state_processing::is_valid_genesis_state;
 use std::path::Path;
 use types::{BeaconState, EthSpec, ForkName};