Update public parameters for 'product_variation' and 'shop_coupon' CPTs

Update 'public' parameters for 'product_variation' and 'shop_coupon' to 'false' and update 'query_var' parameter for 'product_variation' to false.
Merge pull request #3111 from krogsgard/master

Update CPT parameters for 'product_variation' and 'shop_coupon'