wordpress-remove-random-password.php

<?php 

add_filter('random_password', 'endo_disable_random_password', 10, 4);

function endo_disable_random_password($password, $length, $special_chars, $extra_special_chars)
{
    global $action;

    if ('wp-login.php' === $GLOBALS['pagenow'] && in_array($action, ['rp', 'resetpass', 'login'])) {
        $password = '';
    }

    return $password;
}