CI: fix flake in test_penalty_htlc_tx_timeout

Make sure l1 sees the l5 channel!

```
2025-04-29T02:39:42.1086397Z         # now we send two 'sticky' htlcs, l1->l5 + l4->l1
2025-04-29T02:39:42.1086837Z         amt = 10**8 // 2
2025-04-29T02:39:42.1087231Z         sticky_inv_1 = l5.rpc.invoice(amt, '2', 'sticky')
2025-04-29T02:39:42.1087767Z >       route = l1.rpc.getroute(l5.info['id'], amt, 1)['route']
2025-04-29T02:39:42.1088126Z 
2025-04-29T02:39:42.1088279Z tests/test_closing.py:1432: 
...
2025-04-29T02:39:42.1111693Z         elif "error" in resp:
2025-04-29T02:39:42.1111976Z >           raise RpcError(method, payload, resp['error'])
2025-04-29T02:39:42.1113258Z E           pyln.client.lightning.RpcError: RPC call failed: method: getroute, payload: {'id': '032cf15d1ad9c4a08d26eab1918f732d8ef8fdc6abb9640bf3db174372c491304e', 'amount_msat': 50000000, 'riskfactor': 1, 'cltv': 9}, error: {'code': -32602, 'message': '032cf15d1ad9c4a08d26eab1918f732d8ef8fdc6abb9640bf3db174372c491304e: unknown destination node_id (no public channels?)'}
```

Signed-off-by: Rusty Russell <[email protected]>

Author: rustyrussell

tests/test_closing.py

@@ -1414,8 +1414,12 @@ def test_penalty_htlc_tx_timeout(node_factory, bitcoind, chainparams, anchors):
 
     l1, l2, l3, l4, l5 = node_factory.get_nodes(5, opts=opts)
 
-    node_factory.join_nodes([l1, l2, l3, l4], wait_for_announce=True)
-    node_factory.join_nodes([l3, l5], wait_for_announce=True)
+    node_factory.join_nodes([l1, l2, l3, l4])
+    node_factory.join_nodes([l3, l5])
+    bitcoind.generate_block(5)
+    # Make sure all nodes see all channels!
+    for n in (l1, l2, l3, l4, l5):
+        wait_for(lambda: len(n.rpc.listchannels()['channels']) == 4 * 2)
 
     channel_id = first_channel_id(l2, l3)