WooCommerce Groups 2.8.0

* WordPress 5.7 compatible.
* WooCommerce 5.1 compatible.
* WooCommerce 5.0 copmatible.
* Fixed a deprecated use of the PHP ternary operator, unparenthesized `a ? b : c ? d : e` is deprecated as of PHP 7.4.0.
* Updated woo-includes.

* WordPress 5.5 compatible.
* WooCommerce 4.7 compatible.
* As of this release, at least WooCommerce 3.x is required and at least WooCommerce 4.x will be required for future updates.
* Removed backwards-compatibility for use of get_product().
* Removed backwards-compatibility for use of woocommerce_get_formatted_variation().
* Minor improvement on the extension's settings for clarity.

* WordPress 5.5 compatible.
* WooCommerce 4.4 compatible.
* Fixed an incorrect variable reference when rendering subscription information for variable subscriptions.
* Added the groups_woocommerce_user_show_subscriptions_options filter.
* Showing all columns for group subscriptions in user profile instead of limited set.
* Fixed minor missing variable initializations (did not cause functional impact).
* Fixed missing translations.
* Updated translations.