WooCommerce Freshdesk 1.3.1

* Tweak - Remove legacy code.
* Tweak - WC 4.0 compatibility.

* Tweak - WC 3.9 compatibility

* Fix - Remove use of deprecated email_order_items_table function for WooCommerce 3.0+.
* Fix - Sanitize ticket form fields and remove slashes from Subject and Description.
* Fix - Remove use of deprecated $order->order_date property.
* Tweak - Fix language on Integration page.
* Fix - Update postmakepot command to avoid errors when generating a POT file.
* Tweak - WC 3.8 compatibility.