f use Vec::append as suggested by Jeff

Author: TheBlueMatt

lightning/src/ln/channelmanager.rs

@@ -2991,10 +2991,7 @@ impl<ChanSigner: ChannelKeys, M: Deref + Sync + Send, T: Deref + Sync + Send, K:
 			channel_state.by_id.retain(|_, channel| {
 				let res = channel.block_connected(header, height, txn_matched, indexes_of_txn_matched);
 				if let Ok((chan_res, mut timed_out_pending_htlcs)) = res {
-					timed_out_htlcs.reserve(timed_out_pending_htlcs.len());
-					for (htlc_src, payment_hash, value) in timed_out_pending_htlcs.drain(..) {
-						timed_out_htlcs.push((htlc_src, payment_hash, value));
-					}
+					timed_out_htlcs.append(&mut timed_out_pending_htlcs);
 					if let Some(funding_locked) = chan_res {
 						pending_msg_events.push(events::MessageSendEvent::SendFundingLocked {
 							node_id: channel.get_their_node_id(),