Remove unused dependency hex

Author: Gabriel Comte

json/Cargo.toml

@@ -20,6 +20,5 @@ path = "src/lib.rs"
 [dependencies]
 serde = { version = "1", features = [ "derive" ] }
 serde_json = "1"
-hex = "0.3"
 
 bitcoin = { version = "0.26", features = [ "use-serde" ] }