vanityaddr: Enable async feature in darkfi-sdk.

bin/vanityaddr/Cargo.toml

@@ -13,6 +13,6 @@ bs58 = "0.5.0"
 clap = {version = "4.3.24", features = ["derive"]}
 ctrlc = "3.4.0"
 darkfi = {path = "../../", features = ["util"]}
-darkfi-sdk = {path = "../../src/sdk"}
+darkfi-sdk = {path = "../../src/sdk", features = ["async"]}
 rand = "0.8.5"
 rayon = "1.7.0"