Removed an obsolete lint control annotation.

The lint issue that made the workaround necessary has been resolved.

quinn/examples/server.rs

@@ -60,7 +60,6 @@ fn main() {
 }
 
 #[tokio::main]
-#[allow(clippy::field_reassign_with_default)] // https://github.com/rust-lang/rust-clippy/issues/6527
 async fn run(options: Opt) -> Result<()> {
     let (certs, key) = if let (Some(key_path), Some(cert_path)) = (&options.key, &options.cert) {
         let key = fs::read(key_path).context("failed to read private key")?;