ssh-key: bump ed25519-dalek dependency to v3 (#572)

Release PR: dalek-cryptography/curve25519-dalek#916

Author: tarcieri

Cargo.lock

@@ -29,7 +29,7 @@ zeroize = { version = "1.9", default-features = false }
 argon2 = { version = "0.6.0-rc.8", optional = true, default-features = false, features = ["alloc"] }
 bcrypt-pbkdf = { version = "0.11", optional = true, default-features = false, features = ["alloc"] }
 dsa = { version = "0.7", optional = true, default-features = false, features = ["hazmat"] }
-ed25519-dalek = { version = "3.0.0-rc.1", optional = true, default-features = false }
+ed25519-dalek = { version = "3", optional = true, default-features = false }
 hex = { version = "0.4", optional = true, default-features = false, features = ["alloc"] }
 hmac = { version = "0.13", optional = true }
 p256 = { version = "0.14.0-rc.15", optional = true, default-features = false, features = ["ecdsa"] }