deps: add missing feature to secp256k1

Author: OverOrion

crates/nostr/Cargo.toml

@@ -58,7 +58,7 @@ cbc = { version = "0.1", features = ["alloc"], optional = true }
 log = "0.4" # no_std compatible by-default
 nostr-ots = { version = "0.2", optional = true }
 reqwest = { version = "0.11", default-features = false, features = ["json", "rustls-tls-webpki-roots", "socks"], optional = true }
-secp256k1 = { version = "0.27", default-features = false }
+secp256k1 = { version = "0.27", default-features = false, features = ["serde"] }
 
 serde = { version = "1.0", features = ["derive"], default-features = false, optional = true }
 serde_json = { version = "1.0", optional = true, default-features = false }