**Apache Airflow version**: 2.1.1

**What happened**:

The rendered templates screen doesn't show the operator arguments for TaskFlow API operators.
![image](https://user-images.githubusercontent.com/72943478/125486179-f6dde0be-9f60-4aca-831a-5cfd16e7f006.png)

**What you expected to happen**:

Should show the arguments after any templates have been rendered.

**How to reproduce it**:

Will happen for any `@task` decorated operator.

**Anything else we need to know**:

This issue appears on a number of operators.  Possible solution is to modify the "get_python_source" in utils/code_utils.py to handle list and dict. This would cause any operator that using py as the renderer to handle lists and dicts.  Possibly something like:
```
    if isinstance(x, list):
        return [str(v) for v in x]

    if isinstance(x, dict):
        return {k: str(v) for k, v in x.items()}
```
The converting values to strings seems necessary in order to avoid errors when this is passed to the pygments lexer.
![image](https://user-images.githubusercontent.com/72943478/125494716-01cf0c11-9e5f-45fa-afe2-4f99409edefc.png)

airflow/www/views.py
"""Get rendered k8s yaml."""
        if not settings.IS_K8S_OR_K8SCELERY_EXECUTOR:
            abort(404)
        dag_id = request.args.get('dag_id')
        task_id = request.args.get('task_id')
        execution_date = request.args.get('execution_date')
        dttm = timezone.parse(execution_date)
        form = DateTimeForm(data={'execution_date': dttm})
        root = request.args.get('root', '')
        logging.info("Retrieving rendered templates.")
        dag = current_app.dag_bag.get_dag(dag_id)
        task = dag.get_task(task_id)
        ti = models.TaskInstance(task=task, execution_date=dttm)
        pod_spec = None
        try:
            pod_spec = ti.get_rendered_k8s_spec()
        except AirflowException as e:
            msg = "Error rendering Kubernetes POD Spec: " + escape(e)
            if e.__cause__:
                msg += Markup("<br><br>OriginalError: ") + escape(e.__cause__)
            flash(msg, "error")
        except Exception as e:
            flash("Error rendering Kubernetes Pod Spec: " + str(e), "error")