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/ssz_static.rs

@@ -2,7 +2,7 @@ use super::*;
 use crate::case_result::compare_result;
 use crate::cases::common::SszStaticType;
 use crate::decode::{snappy_decode_file, yaml_decode_file};
-use serde_derive::Deserialize;
+use serde::Deserialize;
 use ssz::Decode;
 use tree_hash::TreeHash;
 use types::{BeaconBlock, BeaconState, ForkName, Hash256, SignedBeaconBlock};