### What do you see as an issue?

The documentation for zombie tasks https://airflow.apache.org/docs/apache-airflow/stable/core-concepts/tasks.html#zombie-undead-tasks is a bit abstract at the moment. There is a scope for enhancing the document by explaining how Airflow detects tasks as zombies

### Solving the problem

We can enhance the documentation by translating this query https://github.com/astronomer/airflow/blob/main/airflow/jobs/scheduler_job_runner.py#L1721 to a layman readable text in our documentation.

### Anything else

It might also help to add developer contribution steps to reproduce zombies locally.

### Are you willing to submit PR?

- [ ] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)

dag_id,
                    current_active_tasks_per_dag,
                    max_active_tasks_per_dag_limit,
                )
                if current_active_tasks_per_dag >= max_active_tasks_per_dag_limit:
                    self.log.info(
                        "Not executing %s since the number of tasks running or queued "
                        "from DAG %s is >= to the DAG's max_active_tasks limit of %s",
                        task_instance,
                        dag_id,
                        max_active_tasks_per_dag_limit,
                    )
                    starved_dags.add(dag_id)
                    continue
                if task_instance.dag_model.has_task_concurrency_limits:
                    
                    
                    serialized_dag = self.dagbag.get_dag(dag_id, session=session)
                    
                    if not serialized_dag:
                        self.log.error(
                            "DAG '%s' for task instance %s not found in serialized_dag table",
                            dag_id,
                            task_instance,
                        )
                        session.execute(
                            update(TI)
                            .where(TI.dag_id == dag_id, TI.state == TaskInstanceState.SCHEDULED)
                            .values(state=TaskInstanceState.FAILED)
                            .execution_options(synchronize_session="fetch")