Exclude WooCommerce shipping class URLs from purge

[webtrainingwheels]

When a customer has defined shipping classes in WooCommerce, they are automatically included in WPR's purge list.

The problem is that the URL contains a query string, like this:
https://example.com/?product_shipping_class=korge

This gets converted to https://example.com/ and therefore causes the cache for the entire site to be deleted when a product is updated.

ticket ref: https://secure.helpscout.net/conversation/420919215/47500/?folderId=377611
shipping class ref: https://github.com/woocommerce/woocommerce/blob/master/includes/class-wc-post-types.php