Correct dated comment

src/config.rs

@@ -9,7 +9,7 @@ pub trait ConfigBuilderExt {
     /// This configures the platform's trusted certs, as implemented by
     /// rustls-native-certs
     ///
-    /// This will return None if no valid certs were found. In that case,
+    /// This will return an error if no valid certs were found. In that case,
     /// it's recommended to use `with_webpki_roots`.
     #[cfg(feature = "rustls-native-certs")]
     #[cfg_attr(docsrs, doc(cfg(feature = "rustls-native-certs")))]