Fix flake: `test_increment_active_slots_with_decay_slots_decay_over_time`

### Bug summary


[example failure](https://github.com/PrefectHQ/prefect/actions/runs/11922056701/attempts/1)
```
FAILED tests/server/models/test_concurrency_limits_v2.py::test_increment_active_slots_with_decay_slots_decay_over_time - assert not True
```

### Version info

```Text
main
```


### Additional context

_No response_