Fix CI mypy error: "WorkerFactory" has no attribute "app_config"
Fix type checking on WorkerLoop.loop method, when tryin to access the worker_factory's attribute app_config.

This PR fixes an issue introduced by:
- #774

```
src/datasets_based/worker_loop.py:100: error: "WorkerFactory" has no attribute "app_config"
```
Fix CI mypy error: "WorkerFactory" has no attribute "app_config": Fix type checking on WorkerLoop.loop method, when tryin to access the worker_factory's attribute app_config.

This PR fixes an issue introduced by:
- #774

```
src/datasets_based/worker_loop.py:100: error: "WorkerFactory" has no attribute "app_config"
```