### 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
#
            
            
            
            
            
            
            
            _operator_link_class_path, data = list(_operator_links_source.items())[0]
            if _operator_link_class_path in get_operator_extra_links():
                single_op_link_class = import_string(_operator_link_class_path)
            elif _operator_link_class_path in plugins_manager.registered_operator_link_classes:
                single_op_link_class = plugins_manager.registered_operator_link_classes[
                    _operator_link_class_path
                ]
            else:
                log.error("Operator Link class %r not registered", _operator_link_class_path)
                return {}
            op_predefined_extra_link: BaseOperatorLink = cattr.structure(data, single_op_link_class)
            op_predefined_extra_links.update({op_predefined_extra_link.name: op_predefined_extra_link})
        return op_predefined_extra_links
    @classmethod
    def _serialize_operator_extra_links(cls, operator_extra_links: Iterable[BaseOperatorLink]):