**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/operators/dataflow.py
self.job_id = job_id
            self.hook.start_python_dataflow(
                job_name=self.job_name,
                variables=formatted_options,
                dataflow=self.py_file,
                py_options=self.py_options,
                py_interpreter=self.py_interpreter,
                py_requirements=self.py_requirements,
                py_system_site_packages=self.py_system_site_packages,
                on_new_job_id_callback=set_current_job_id,
                project_id=self.project_id,
                location=self.location,
            )
    def on_kill(self) -> None:
        self.log.info("On kill.")
        if self.job_id:
            self.hook.cancel_job(job_id=self.job_id, project_id=self.project_id)