Release v0.20.1 (#1624)

- Update `libp2p-kad` CHANGELOG and increment version to 0.20.1.
- Update `libp2p` version to 0.20.1.
- Fix some linter warning in `libp2p-gossipsub` and increment
  version to 0.19.3 and update CHANGELOG.

protocols/gossipsub/src/behaviour.rs

@@ -363,7 +363,7 @@ impl Gossipsub {
                 &self.topic_peers,
                 topic_hash,
                 self.config.mesh_n - added_peers.len(),
-                { |_| true },
+                |_| true,
             );
             added_peers.extend_from_slice(&new_peers);
             // add them to the mesh