add_filter( 'random_password', 'disable_random_password', 10, 2 );
function disable_random_password( $password ) {
$action = isset( $_GET['action'] ) ? $_GET['action'] : '';
if ( 'wp-login.php' === $GLOBALS['pagenow'] && ( 'rp' == $action || 'resetpass' == $action ) ) {
return '';
}
return $password;
}