将 Checkout 区块的空购物车替代内容与新的购物车和迷你购物车的空状态对齐

The Checkout block renders its own empty-cart state with the old copy and layout, in `plugins/woocommerce/client/blocks/assets/js/blocks/checkout/empty-cart/index.js:23`: a cart icon, "Your cart is currently empty!", a sentence, and a "Browse store" button. The Cart and Mini-Cart blocks now show "Your cart is empty" with a "Return to shop" button, since woocommerce/woocommerce#68560.