**Description**

function test_cycle will be collected by pytest if this function is imported in a user-defined test.
Such an error will be emitted as pytest will treat it as a test.
```
test setup failed
file /opt/conda/lib/python3.8/site-packages/airflow/utils/dag_cycle_tester.py, line 27
  def test_cycle(dag):
E       fixture 'dag' not found
>       available fixtures: cache, capfd, capfdbinary, caplog, capsys, capsysbinary, doctest_namespace, monkeypatch, pytestconfig, record_property, record_testsuite_property, record_xml_attribute, recwarn, tmp_path, tmp_path_factory, tmpdir, tmpdir_factory
>       use 'pytest --fixtures [testpath]' for help on them.

```

**Use case / motivation**
This can be simply "fixed" by renaming this function to check_cycle although the user can do it upon importing this function.
This change by airflow will reduce the amount of surprise received by the end-user, and save a large number of debugging hours. 

**Are you willing to submit a PR?**
The changeset is too small to worth the trouble for a PR. 
airflow/models/dagbag.py
"""Prints a report around DagBag loading stats"""
        stats = self.dagbag_stats
        dag_folder = self.dag_folder
        duration = sum((o.duration for o in stats), timedelta()).total_seconds()
        dag_num = sum(o.dag_num for o in stats)
        task_num = sum(o.task_num for o in stats)
        table = tabulate(stats, headers="keys")
        report = textwrap.dedent(
            f"""\n
        -------------------------------------------------------------------
        DagBag loading stats for {dag_folder}
        -------------------------------------------------------------------
        Number of DAGs: {dag_num}
        Total task number: {task_num}
        DagBag parsing time: {duration}
        {table}
        """
        )
        return report
    @provide_session
    def sync_to_db(self, session: Optional[Session] = None):