Bump x25519-dalek to stable 2 (#492)

Author: pinkforest

dtls/Cargo.toml

@@ -31,7 +31,7 @@ aes-gcm = "0.10.1"
 ccm = "0.3.0"
 tokio = { version = "1.19", features = ["full"] }
 async-trait = "0.1.56"
-x25519-dalek = { version = "2.0.0-rc.2", features = ["static_secrets"] }
+x25519-dalek = { version = "2", features = ["static_secrets"] }
 x509-parser = "0.13.2"
 der-parser = "8.1"
 rcgen = "0.10.0"