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>

beacon_node/store/src/metadata.rs

@@ -1,5 +1,5 @@
 use crate::{DBColumn, Error, StoreItem};
-use serde_derive::{Deserialize, Serialize};
+use serde::{Deserialize, Serialize};
 use ssz::{Decode, Encode};
 use ssz_derive::{Decode, Encode};
 use types::{Checkpoint, Hash256, Slot};