Update rustls-native-certs and prepare 0.20

Author: ctz

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "hyper-rustls"
-version = "0.19.2"
+version = "0.20.0"
 edition = "2018"
 authors = ["Joseph Birr-Pixton <jpixton@gmail.com>"]
 license = "Apache-2.0/ISC/MIT"
@@ -16,7 +16,7 @@ ct-logs = { version = "^0.6", optional = true }
 futures-util = "0.3.1"
 hyper = { version = "0.13.0", default-features = false }
 rustls = "0.17"
-rustls-native-certs = { version = "0.2.1", optional = true }
+rustls-native-certs = { version = "0.3.0", optional = true }
 tokio = "0.2.4"
 tokio-rustls = "0.13.0"
 webpki = "0.21.0"