Removes reference to secret key (#303)

Author: lmac-1

docs/docs/welcome/getting-started-client-mode.mdx

@@ -13,7 +13,7 @@ or
 yarn add use-shopping-cart
 ```
 
-The package needs to be configured with your account's secret key, which is available in the [Stripe Dashboard](https://dashboard.stripe.com/apikeys). Require it with the key's value.
+The package needs to be configured with your account's publishable key, which is available in the [Stripe Dashboard](https://dashboard.stripe.com/apikeys). Require it with the key's value.
 
 At the root level of your app, wrap your root component in the `<CartProvider />`