Deleting task instance from UI deletes Dag Run too

[jsanko9]

Apache Airflow version:
2.1.0, also 2.1.1

Kubernetes version (if you are using kubernetes) (use kubectl version):
1.19.6

Environment:
On-premise Cluster
Official Docker Image with Python 3.8

What happened:
When working in '/taskinstance/list/' view and clicking on 'Delete record' as an admin. It deletes not only task instance but also whole Dag run.

What you expected to happen:
To be honest not sure, probably task to be requeued/cleared or warning that dag will be removed too.

How to reproduce it:
Any running dag, simply removing task instance trough UI

Anything else we need to know:
In backend DB (Postgres12), DAG run record is not deleted. but dag run's dag_id and execution_date was set to

How often does this problem occur? Once? Every time etc?
Every time

[boring-cyborg]

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[kaxil]

closed by #17719