frappe/frappe/templates/emails/password_update.html

<h3>{{_("Password Update Notification")}}</h3>
<p>{{_("Dear")}} {{ first_name }}{% if last_name %} {{ last_name}}{% endif %},</p>
<p>{{_("Your password has been updated. Here is your new password")}}: <b>{{ new_password }}</b></p>
<p>{{_("Thank you")}},<br>
{{ user_fullname }}</p>