Иконка задана тут
.woocommerce a.add_to_cart_button.button:before, .woocommerce a.product_type_variable.button:before, .woocommerce a.product_type_grouped.button:before, .woocommerce a.product_type_simple.button:before, .woocommerce div.product form.cart button.single_add_to_cart_button:before { content: "\f07a"; cursor: pointer; /* font-family: FontAwesome; */ font-size: 13px; font-style: normal; font-weight: normal; line-height: 1; padding-right: 4px; position: relative; text-shadow: none; -webkit-font-smoothing: antialiased; color:inherit; speak: none; }
достаточно будет удалить
.woocommerce div.product form.cart button.single_add_to_cart_button:before