pytest: expect slow commands with giant commando test

```
2025-12-10T02:51:06.2435409Z [gw1] [ 77%] ERROR tests/test_plugin.py::test_commando
...lightningd-1: had BROKEN messages
...
2025-12-10T03:00:26.0440311Z lightningd-1 2025-12-10T02:51:01.548Z UNUSUAL jsonrpc#69: That's weird: Request checkrune took 5961 milliseconds
```

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

Author: rustyrussell

tests/test_plugin.py

@@ -2844,7 +2844,8 @@ def test_plugin_shutdown(node_factory):
 
 def test_commando(node_factory, executor):
     l1, l2 = node_factory.line_graph(2, fundchannel=False,
-                                     opts={'log-level': 'io'})
+                                     # Under valgrind, checkrune of 400k command can be slow!
+                                     opts={'log-level': 'io', 'broken_log': "That's weird: Request .* took"})
 
     rune = l1.rpc.createrune()['rune']