**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
"""Formats hidden fields"""
        key = self.get('key')
        val = self.get('val')
        if secrets_masker.should_hide_value_for_key(key):
            return Markup('*' * 8)
        if val:
            return val
        else:
            return Markup('<span class="label label-danger">Invalid</span>')
    formatters_columns = {
        'val': hidden_field_formatter,
    }
    validators_columns = {'key': [validators.DataRequired()]}
    def prefill_form(self, form, request_id):
        if secrets_masker.should_hide_value_for_key(form.key.data):
            form.val.data = '*' * 8
    @action('muldelete', 'Delete', 'Are you sure you want to delete selected records?', single=False)
    def action_muldelete(self, items):