I’m getting the following error for the href value within the Cart Menu Item generated by GP:
<b>Notice</b>: WC_Cart::get_cart_url is <strong>deprecated</strong> since version 2.5! Use wc_get_cart_url instead. in <b>/.../public_html/staging/wp-includes/functions.php</b> on line <b>3831</b><br />
I changed WC()->cart->get_cart_url() in the functions.php file to wc_get_cart_url() and the deprecation notice went away. I’m using the default WC AJAX functions (Enable AJAX add to cart buttons on archives) and the Menu Cart value still updates with AJAX using the wc_get_cart_url() function.
I was looking at the code from a standalone WC Cart Menu item plugin (which worked for me), and they used this wc_get_cart_url() with a WC version check.