**Apache Airflow version**: 2.0.1

**What happened**:

The operator fails at the last step, after successfully refreshing the workbook with this error:
```
tableauserverclient.server.endpoint.exceptions.ServerResponseError: 

        401002: Unauthorized Access
                Invalid authentication credentials were provided.
```

**What you expected to happen**:
It should not fail, like when we use the username/password authentication method (instead of personal_access_token)

<!-- What do you think went wrong? -->

Tableau server does not allow concurrent connections when using personal_access_token https://github.com/tableau/server-client-python/issues/717
The solution would be redesigning completely the operator to only call the hook once.
My quick fix was to edit this in TableauHook:

```
    def __exit__(self, exc_type: Any, exc_val: Any, exc_tb: Any) -> None:
        pass
```

**How to reproduce it**:

Run this operator TableauRefreshWorkbookOperator using Tableau personal_access_token authentication (token_name, personal_access_token).

tests/providers/tableau/operators/test_tableau_refresh_workbook.py
"""
    Test class for TableauRefreshWorkbookOperator
    """
    def setUp(self):
        """
        setup
        """
        self.mocked_workbooks = []
        for i in range(3):
            mock_workbook = Mock()
            mock_workbook.id = i
            mock_workbook.name = f'wb_{i}'
            self.mocked_workbooks.append(mock_workbook)
        self.kwargs = {'site_id': 'test_site', 'task_id': 'task', 'dag': None}
    @patch('airflow.providers.tableau.operators.tableau_refresh_workbook.TableauHook')
    def test_execute(self, mock_tableau_hook):
        """
        Test Execute
        """
        mock_tableau_hook.get_all = Mock(return_value=self.mocked_workbooks)
        mock_tableau_hook.return_value.__enter__ = Mock(return_value=mock_tableau_hook)
        operator = TableauRefreshWorkbookOperator(blocking=False, workbook_name='wb_2', **self.kwargs)
        job_id = operator.execute(context={})
        mock_tableau_hook.server.workbooks.refresh.assert_called_once_with(2)
        assert mock_tableau_hook.server.workbooks.refresh.return_value.id == job_id
    @patch('airflow.providers.tableau.sensors.tableau_job_status.TableauJobStatusSensor')
    @patch('airflow.providers.tableau.operators.tableau_refresh_workbook.TableauHook')
    def test_execute_blocking(self, mock_tableau_hook, mock_tableau_job_status_sensor):