**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).

airflow/providers/tableau/operators/tableau_refresh_workbook.py
for workbook in tableau_hook.get_all(resource_name='workbooks'):
            if workbook.name == self.workbook_name:
                self.log.info('Found matching workbook with id %s', workbook.id)
                return workbook
        raise AirflowException(f'Workbook {self.workbook_name} not found!')
    def _refresh_workbook(self, tableau_hook: TableauHook, workbook_id: str) -> str:
        job = tableau_hook.server.workbooks.refresh(workbook_id)
        self.log.info('Refreshing Workbook %s...', self.workbook_name)
        return job.id