### Apache Airflow version

2.1.3 (latest released)

### Operating System

macOS Big Sur 11.3.1

### Versions of Apache Airflow Providers

n/a

### Deployment

Astronomer

### Deployment details

default Astronomer deployment with some test DAGs

### What happened

In the UI for DAGRuns there are checkboxes that allow multiple DAGRuns to be selected.

![image](https://user-images.githubusercontent.com/89415310/133841290-94cda771-9bb3-4677-8530-8c2861525719.png)

Within the Actions menu on this same view, there is a Delete option which allows multiple DAGRuns to be deleted at the same time.

![image](https://user-images.githubusercontent.com/89415310/133841362-3c7fc81d-a823-4f41-8b1d-64be425810ce.png)

Task instance view on the UI does not offer the same option, even though Task Instances can be individually deleted with the trash can button.

![image](https://user-images.githubusercontent.com/89415310/133841442-3fee0930-a6bb-4035-b172-1d10b85f3bf6.png)


### What you expected to happen

I expect that the Task Instances can also be bulk deleted, in the same way that DAGRuns can be.

### How to reproduce

Open up Task Instance and DAGRun views from the Browse tab and compare the options in the Actions dropdown menus.

### Anything else

_No response_

### 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/www/views.py
"""Process form data."""
        conn_type = form.data['conn_type']
        conn_id = form.data["conn_id"]
        extra = {
            key: form.data[key]
            for key in self.extra_fields
            if key in form.data and key.startswith(f"extra__{conn_type}__")
        }
        
        
        extra_conn_params = form.data.get("extra")
        if extra_conn_params:
            try:
                extra.update(json.loads(extra_conn_params))
            except (JSONDecodeError, TypeError):
                flash(
                    Markup(
                        "<p>The <em>Extra</em> connection field contained an invalid value for Conn ID: "
                        f"<q>{conn_id}</q>.</p>"
                        "<p>If connection parameters need to be added to <em>Extra</em>, "
                        "please make sure they are in the form of a single, valid JSON object.</p><br>"
                        "The following <em>Extra</em> parameters were <b>not</b> added to the connection:<br>"
                        f"{extra_conn_params}",
                    ),
                    category="error",
                )
        if extra.keys():
            form.extra.data = json.dumps(extra)
    def prefill_form(self, form, pk):