Listen on ipv4, no automagic v6-to-v4 mapping

Index: crates/common/src/config/server/listener.rs
--- crates/common/src/config/server/listener.rs.orig
+++ crates/common/src/config/server/listener.rs
@@ -68,7 +68,7 @@ impl Listeners {
                     object: NetworkListener {
                         bind: Map::new(vec![
                             SocketAddr::from_str(&format!(
-                                "[::]:{}",
+                                "0.0.0.0:{}",
                                 std::env::var("STALWART_RECOVERY_MODE_PORT")
                                     .ok()
                                     .and_then(|p| p.parse::<u16>().ok())
