feat: do not use webpki roots in main example

examples/main.rs

@@ -37,7 +37,6 @@ async fn main() -> Result<(), tokio_gemini::LibError> {
             .build()
     } else {
         tokio_gemini::Client::builder()
-            .with_webpki_roots() // TODO: do we really need them?
             .with_selfsigned_cert_verifier(CertVerifier::init().await?)
             .build()
     };