flake: coderd/devtunnel: unknown

Seen here: 
* https://github.com/coder/coder/actions/runs/14401666585/job/40388697534
* https://github.com/coder/coder/actions/runs/14389572858/job/40353614716


Only seen on Windows so far.

```
=== Failed
=== FAIL: coderd/devtunnel TestTunnel/V1 (unknown)

=== FAIL: coderd/devtunnel TestTunnel/V2 (unknown)

=== FAIL: coderd/devtunnel TestTunnel (unknown)
```