Bump to rusttls 0.18.0

Author: Jason Mobarak

Cargo.toml

@@ -17,7 +17,7 @@ appveyor = { repository = "async-std/async-tls" }
 
 [dependencies]
 futures = "0.3.4"
-rustls = "0.17.0"
+rustls = "0.18.0"
 webpki = "0.21.2"
 webpki-roots = "0.19.0"