Fix use of serde_derive

Author: dr-orlovsky

Cargo.lock

@@ -28,7 +28,7 @@ ed25519-dalek = { version = "1.0", optional = true }
 lnpbp_secp256k1zkp = { version = "0.9.0-alpha.1", optional = true }
 chrono = { version = "0.4", optional = true }
 half = { version = "2.1", optional = true }
-serde = { version = "1.0", optional = true }
+serde = { version = "1.0", features = ["derive"], optional = true }
 monero = { version = "0.18", optional = true }
 
 [dev-dependencies]