### Apache Airflow version

2.1.3 (latest released)

### Operating System

Debian Buster

### Versions of Apache Airflow Providers

_No response_

### Deployment

Managed Services (Astronomer, Composer, MWAA etc.)

### Deployment details

Running `quay.io/astronomer/ap-airflow:2.1.3-buster` Docker image

### What happened

In the task attributes view of a BashOperator, the `template_ext` row doesn't show any value, while I would expect to see `('.sh', '.bash')`.

![image](https://user-images.githubusercontent.com/6249654/131467817-8620f68d-0f3d-491d-ad38-cbf5b91cdcb3.png)


### What you expected to happen

Expect to see correct `template_ext` value

### How to reproduce

Run a BashOperator and browse to Instance Details --> scroll down to `template_ext` row

### Anything else

Spent a little time trying to figure out what could be the reason, but haven't found the problem yet. Therefore created issue to track.

### Are you willing to submit PR?

- [X] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)

airflow/serialization/serialized_objects.py
"""
    Returns operator extra links - both the ones that are built in and the ones that come from
    the providers.
    :return: set of extra links
    """
    _OPERATOR_EXTRA_LINKS.update(ProvidersManager().extra_links_class_names)
    return _OPERATOR_EXTRA_LINKS
def encode_relativedelta(var: relativedelta.relativedelta) -> Dict[str, Any]:
    encoded = {k: v for k, v in var.__dict__.items() if not k.startswith("_") and v}
    if var.weekday and var.weekday.n:
        
        encoded['weekday'] = [var.weekday.weekday, var.weekday.n]
    elif var.weekday:
        encoded['weekday'] = [var.weekday.weekday]
    return encoded
def decode_relativedelta(var: Dict[str, Any]) -> relativedelta.relativedelta: