**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/hooks/tableau.py
tableau_auth = TableauAuth(
            username=self.conn.login, password=self.conn.password, site_id=self.site_id
        )
        return self.server.auth.sign_in(tableau_auth)
    def _auth_via_token(self) -> Auth.contextmgr:
        tableau_auth = PersonalAccessTokenAuth(
            token_name=self.conn.extra_dejson['token_name'],
            personal_access_token=self.conn.extra_dejson['personal_access_token'],
            site_id=self.site_id,
        )
        return self.server.auth.sign_in_with_personal_access_token(tableau_auth)
    def get_all(self, resource_name: str) -> Pager:
        """
        Get all items of the given resource.
        .. see also:: https://tableau.github.io/server-client-python/docs/page-through-results
        :param resource_name: The name of the resource to paginate.
            For example: jobs or workbooks
        :type resource_name: str
        :return: all items by returning a Pager.
        :rtype: tableauserverclient.Pager
        """
        resource = getattr(self.server, resource_name)
        return Pager(resource.get)