reckless: process hung in CI

I tried reckless through the recklessrpc plugin like this:

```python
l1 = node_factory.get_node()
l1.rpc.call("reckless", ["source", "remove", "https://github.com/lightningd/plugins"])
```

and this works on my machine with CLN v25.12 just fine but on the CI, also v25.12, i get:

```
lightningd-1 2025-12-05T16:07:44.179Z DEBUG plugin-recklessrpc: calling: reckless -v --json -l /tmp/ltests-lpr9tg9f/test_program_1/lightning-1/ --network regtest source remove https://github.com/lightningd/plugins (null)
lightningd-1 2025-12-05T16:07:44.271Z DEBUG plugin-recklessrpc: confirming config creation
lightningd-1 2025-12-05T16:07:44.291Z DEBUG plugin-recklessrpc: reckless failed to exit, killing now.
```

```
error: {'code': -3, 'message': 'reckless process hung'}
```

Now if i try this in the CI:
```python
l1 = node_factory.get_node()

ln_dir = str(Path(l1.info["lightning-dir"]).parent)
subprocess.run(
[
"reckless",
"-v",
"--json",
"-l",
ln_dir,
"--network",
"regtest",
"source",
"remove",
"https://github.com/lightningd/plugins",
],
input="Y\n",
text=True,
capture_output=True,
)
```

it works.