Remove add_action from plugin

I use this plugin. Is for auto expire user on specific date.

I want to add this action add_action(‘edit_user_profile’, array($this, ‘extra_user_profile_fields’)) when is_admin only because i have a conflict with an other plugin. I have try this to source code:

if (is_admin) {
add_action('edit_user_profile', array($this, 'extra_user_profile_fields'))
}

and all work well! But i want to add a function to child theme.

class Expire_User_Admin
{

    var $settings = null;

    public function __construct()
    {
        $this->settings = new Expire_User_Settings();

        // Admin Actions
        add_action('admin_init', array($this, 'expire_user_now'));

        // Profile Fields

        add_action('show_user_profile', array($this, 'extra_user_profile_fields'));
        add_action('edit_user_profile', array($this, 'extra_user_profile_fields'));
        add_action('user_new_form', array($this, 'user_new_form')); 

...
}

So i have try this with no luck. Any thoughts?

add_action('init', 'remove_plugin_action', 9999);
function remove_plugin_action()
{
    $plugin_class = new Expire_User_Admin();    
    remove_action('edit_user_profile', array($plugin_class, 'extra_user_profile_fields'));
    if (is_admin()) {
     add_action('edit_user_profile', array($plugin_class, 'extra_user_profile_fields'));
    }
}

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Author: xiamtoula