Using Deprecated Functions

The plugin has been generating deprecated functions for some time and therefore causing server-side errors.

[Thu Sep 02 12:] [proxy_fcgi:error] [pid 5915:tid 139762656438016] [client ] AH01071: Got error 'PHP message: The WC_Session_Handler::nonce_user_logged_out function is deprecated since version 5.3. Replace with WC_Session_Handler::maybe_update_nonce_user_logged_out.', referer: https://www.com/wp-admin/admin-ajax.php?action=wc_facebook_background_product_sync&nonce=3b1b2fbdf4

[Thu Sep 02 12:] [proxy_fcgi:error] [pid 5915:tid 139762547332864] [client ] AH01071: Got error 'PHP message: The WC_Session_Handler::nonce_user_logged_out function is deprecated since version 5.3. Replace with WC_Session_Handler::maybe_update_nonce_user_logged_out.', referer: https://www.com/wp-admin/admin-ajax.php?action=wc_facebook_background_product_sync&nonce=3b1b2fbdf4

[Fri Sep 03 07:] [proxy_fcgi:error] [pid 12605:tid 139762966968064] [client ] AH01071: Got error 'PHP message: The WC_Session_Handler::nonce_user_logged_out function is deprecated since version 5.3. Replace with WC_Session_Handler::maybe_update_nonce_user_logged_out.', referer: https://www.com/wp-admin/admin-ajax.php?action=wc_facebook_background_product_sync&nonce=89a46bb748