**Apache Airflow version**: 2.1.0

**Browsers**: Chrome and Firefox

**What happened**:

Before upgrading to 2.1.0

![before](https://user-images.githubusercontent.com/14293802/120359517-c1ca1100-c2d5-11eb-95ba-58ccc0a3ac37.png)

After upgrading to 2.1.0

![after](https://user-images.githubusercontent.com/14293802/120359528-c4c50180-c2d5-11eb-8e04-f34846ea2736.png)

**What you expected to happen**:

Show/Edit/Delete under Security -> Users are available

<!-- What do you think went wrong? -->

**How to reproduce it**:

Go to Security -> Users (as an admin of course) 
airflow/www/views.py
end_date=end_date,
                include_subdags=recursive,
                include_parentdag=recursive,
                only_failed=only_failed,
                dry_run=True,
            )
        except AirflowException as ex:
            flash(str(ex), 'error')
            return redirect(origin)
        if not tis:
            flash("No task instances to clear", 'error')
            response = redirect(origin)
        else:
            details = "\n".join(str(t) for t in tis)
            response = self.render_template(
                'airflow/confirm.html',
                endpoint=None,
                message="Here's the list of task instances you are about to clear:",
                details=details,
            )
        return response
    @expose('/clear', methods=['POST'])
    @auth.has_access(
        [
            (permissions.ACTION_CAN_READ, permissions.RESOURCE_DAG),
            (permissions.ACTION_CAN_DELETE, permissions.RESOURCE_TASK_INSTANCE),
        ]
    )
    @action_logging
    def clear(self):