ModifyDefaultUserCreationEmail.php

<?php
add_filter( 'wp_new_user_notification_email', function ( $email, $user, $blogname ) {

    $reset_link = wp_lostpassword_url();

    $email['subject'] = sprintf(
        'Welcome to %s – Set your password',
        $blogname
    );

    $email['message'] = sprintf(
        "Hi %s,\n\n".
        "Thanks for your purchase! We've created your account on %s.\n\n".
        "To access your account and manage your profile, please set your password using the link below:\n\n".
        "%s\n\n".
        "If you didn’t request this, you can safely ignore this email.\n\n".
        "Best regards,\n".
        "%s Team",
        $user->display_name ?: $user->user_login,
        $blogname,
        $reset_link,
        $blogname
    );

    return $email;

}, 10, 3 );