A small add-on that add 1 permission "Disable Lost Password".
If u add it for User or User Group, then they can't use recovery password function.
The error text is set in the phrase "this_group_cannot_lost_passw", you can change it to any other.
If suddenly you have disabled password recovery for the administrator and have forgotten the password of the administrator, you can disable the add-on.
For this file /library/config.php add one line at the end:
$ config ['disableLostOff'] = true;