radicle: Fix required features for `fastrand` — heartwood

The radicle crate would not build on its own with cargo build --package=radicle because some fastrand features were missing.

 cyphernet = { workspace = true, features = ["tor", "dns", "p2p-ed25519"] }
 dunce = { workspace = true }
 fast-glob = { version = "0.3.2" }
 fastrand = { workspace = true }
 fastrand = { workspace = true, features = ["std"] }
 git2 = { workspace = true, features = ["vendored-libgit2"] }
 indexmap = { version = "2", features = ["serde"] }
 localtime = { workspace = true, features = ["serde"] }