enable "ring" feature on rustls

Signed-off-by: Jun Kimura <jun.kimura@datachain.jp>

Author: bluele

modules/remote-attestation/Cargo.toml

@@ -11,7 +11,7 @@ rand = { version = "0.8" }
 hex = { version = "0.4", default-features = false, features = ["alloc"] }
 base64 = { version = "0.22.1", default-features = false, features = ["alloc"] }
 httparse = { version = "1.3", default-features = false }
-rustls = { version = "0.23" }
+rustls = { version = "0.23", features = ["ring"] }
 webpki-roots = { version = "0.26" }
 flex-error = { version = "0.4.4" }
 pem = { version = "3", default-features = false }