Bump elliptic-curve to v0.10; MSRV 1.51+ (#268)

Also updates the following:
- `p256` v0.9
- `p384` v0.8

Cargo.toml

@@ -26,7 +26,7 @@ chrono = "0.4"
 cookie-factory = "0.3"
 der-parser = "5"
 des = "0.7"
-elliptic-curve = "0.9"
+elliptic-curve = "0.10"
 getrandom = "0.1"
 hmac = "0.11"
 log = "0.4"
@@ -35,8 +35,8 @@ num-bigint-dig = { version = "0.7", features = ["rand"], package = "num-bigint-d
 num-traits = "0.2"
 num-integer = "0.1"
 pbkdf2 = { version = "0.8", default-features = false }
-p256 = "0.8"
-p384 = "0.7"
+p256 = "0.9"
+p384 = "0.8"
 pcsc = "2"
 rsa = "0.4"
 secrecy = "0.7"
@@ -50,7 +50,6 @@ zeroize = "1"
 
 [dev-dependencies]
 env_logger = "0.8"
-ring = "0.16.18"
 lazy_static = "1"
 
 [features]