doc(hidden) for TransactionsManager handle only used in tests (#6748)

Co-authored-by: Matthias Seitz <matthias.seitz@outlook.de>

examples/network-txpool.rs

@@ -42,6 +42,9 @@ async fn main() -> eyre::Result<()> {
         .transactions(pool.clone(), transactions_manager_config)
         .split_with_handle();
 
+    // this can be used to interact with the `txpool` service directly
+    let _txs_handle = txpool.handle();
+
     // spawn the network task
     tokio::task::spawn(network);
     // spawn the pool task