fud: Use "rpc" feature for darkfi crate.

script/research/fud/fu/Cargo.toml

@@ -11,7 +11,7 @@ edition = "2021"
 [dependencies]
 async-std = {version = "1.12.0", features = ["attributes"]}
 clap = {version = "3.2.20", features = ["derive"]}
-darkfi = {path = "../../../../", features = ["util"]}
+darkfi = {path = "../../../../", features = ["util", "rpc"]}
 log = "0.4.17"
 serde_json = "1.0.85"
 simplelog = "0.12.0"