docs: update docs across projects following publishable API key change in store routes (#9098)

* docs: update docs across projects following publishable API key change in store routes

* rename env variable

* move subscribe route out of store

www/apps/resources/app/storefront-development/cart/update/page.mdx

@@ -21,7 +21,7 @@ If a customer changes their region, you must update their cart to be associated
 For example:
 
 export const updateRegionHighlights = [
-  ["8", `"new_id"`, "Pass the new chosen region's ID."]
+  ["11", `"new_id"`, "Pass the new chosen region's ID."]
 ]
 
 ```ts highlights={updateRegionHighlights}
@@ -30,6 +30,9 @@ fetch(`http://localhost:9000/store/carts/${cartId}`, {
   method: "POST",
   headers: {
     "Content-Type": "application/json",
+    headers: {
+      "x-publishable-api-key": process.env.NEXT_PUBLIC_MEDUSA_PUBLISHABLE_KEY,
+    },
   },
   body: JSON.stringify({
     region_id: "new_id",
@@ -53,7 +56,7 @@ If a guest customer logs in, you must update the cart to be associated with the
 For example:
 
 export const updateCustomerHighlights = [
-  ["8", `"logged_in_id"`, "Pass the logged-in customer's ID."]
+  ["11", `"logged_in_id"`, "Pass the logged-in customer's ID."]
 ]
 
 ```ts highlights={updateCustomerHighlights}
@@ -62,6 +65,9 @@ fetch(`http://localhost:9000/store/carts/${cartId}`, {
   method: "POST",
   headers: {
     "Content-Type": "application/json",
+    headers: {
+      "x-publishable-api-key": process.env.NEXT_PUBLIC_MEDUSA_PUBLISHABLE_KEY,
+    },
   },
   body: JSON.stringify({
     customer_id: "logged_in_id",