**What happened**:

With the new Backport providers, when calling `DataflowCreatePythonJobOperator` with an empty `py_rerquirments` Dataflow commands always launch inside a virtualenv.

**What you expected to happen**:

The Dataflow command should run locally.


airflow/providers/google/cloud/hooks/dataflow.py
self,
        job_name: str,
        variables: Dict,
        parameters: Dict,
        dataflow_template: str,
        project_id: str,
        append_job_name: bool = True,
        on_new_job_id_callback: Optional[Callable[[str], None]] = None,
        location: str = DEFAULT_DATAFLOW_LOCATION
    ) -> Dict:
        """
        Starts Dataflow template job.
        :param job_name: The name of the job.
        :type job_name: str
        :param variables: Map of job runtime environment options.
            .. seealso::
                For more information on possible configurations, look at the API documentation
                `https://cloud.google.com/dataflow/pipelines/specifying-exec-params
                <https://cloud.google.com/dataflow/docs/reference/rest/v1b3/RuntimeEnvironment>`__
        :type variables: dict
        :param parameters: Parameters fot the template
        :type parameters: dict
        :param dataflow_template: GCS path to the template.