Hi John, actually I worked it out 🙂 This is what I did:
function my_update_acf_license() {
acf_pro_update_license( 'xxxxxxxxxxxxxx' );
}
add_action('init', 'my_update_acf_license');
I think it’s no problem since the theme I’m working on will not be sold as a premium theme, so the code won’t be publicized. Thanks for your hint!