Fix off-by-one for unfunded channel peers

When accepting channels manually, it would
fail if the # of peers without funded channels
was == `MAX_UNFUNDED_CHANNEL_PEERS`, however,
it should fail if the # of peers > `MAX_UNFUNDED_CHANNEL_PEERS`.

Author: elnosh

lightning/src/ln/channel_open_tests.rs

@@ -110,7 +110,7 @@ fn test_0conf_limiting() {
 	};
 
 	// First, get us up to MAX_UNFUNDED_CHANNEL_PEERS so we can test at the edge
-	for _ in 0..MAX_UNFUNDED_CHANNEL_PEERS - 1 {
+	for _ in 0..MAX_UNFUNDED_CHANNEL_PEERS {
 		let random_pk = PublicKey::from_secret_key(
 			&nodes[0].node.secp_ctx,
 			&SecretKey::from_slice(&nodes[1].keys_manager.get_secure_random_bytes()).unwrap(),

lightning/src/ln/channelmanager.rs

@@ -10569,7 +10569,7 @@ This indicates a bug inside LDK. Please report this error at https://github.com/
 			// If this peer already has some channels, a new channel won't increase our number of peers
 			// with unfunded channels, so as long as we aren't over the maximum number of unfunded
 			// channels per-peer we can accept channels from a peer with existing ones.
-			if is_only_peer_channel && peers_without_funded_channels >= MAX_UNFUNDED_CHANNEL_PEERS {
+			if is_only_peer_channel && peers_without_funded_channels > MAX_UNFUNDED_CHANNEL_PEERS {
 				let send_msg_err_event = MessageSendEvent::HandleError {
 					node_id: channel.context().get_counterparty_node_id(),
 					action: msgs::ErrorAction::SendErrorMessage {