The URL of the ACF page has changed to this:
edit.php?post_type=acf-field-group
So updating the function will make it work again:
function remove_acf_menu(){
global $current_user;
if ($current_user->user_login!='admin'){
remove_menu_page( 'edit.php?post_type=acf-field-group' );
}
}
add_action( 'admin_menu', 'remove_acf_menu', 100 );
And just a general tip – please do no use “Admin” as the admin username of your wordpress site. It’s a security thing…