backend: fix pair blocking on update state

gamestream-webtransport-proxy/src/pair.rs

@@ -457,6 +457,9 @@ impl crate::server::Server {
             );
         }
 
+        // Release the reader so we can create a writer
+        drop(reader);
+
         match self.state.write().await.add_server(server) {
             Ok(_) => (),
             Err(e) => {