Use then instead of then_some when checking upnp_enabled to avoid useless UPnP query (#6170)

* Use `then` instead of `then_some` when checking `upnp_enabled` to avoid useless UPnP query

Author: dknopik

beacon_node/lighthouse_network/src/service/mod.rs

@@ -385,7 +385,7 @@ impl<E: EthSpec> Network<E> {
         let upnp = Toggle::from(
             config
                 .upnp_enabled
-                .then_some(libp2p::upnp::tokio::Behaviour::default()),
+                .then(libp2p::upnp::tokio::Behaviour::default),
         );
         let behaviour = {
             Behaviour {