Right practice to edit WP reset password email

The filter is there so you don’t need to edit wp-login.php, simply use add_filter.

Put something like

function change_password_reset_mail_body($message, $key, $user_login, $user_data) {
    return "click here: " . network_site_url( "wp-login.php?action=rp&key=$key&login=" . rawurlencode( $user_login ), 'login' );
}

add_filter("retrieve_password_message", "change_password_reset_mail_body", 10, 4)

In your theme’s functions.php.