fix(cloudflare): use the code for the geolocation region (#625)

Use the ISO 3166-2 region code rather than the fullname.
See:
- https://developers.cloudflare.com/workers/runtime-apis/request/
- https://vercel.com/guides/geo-ip-headers-geolocation-vercel-functions#geolocation-headers

packages/open-next/src/overrides/wrappers/cloudflare.ts

@@ -6,7 +6,7 @@ import type { MiddlewareOutputEvent } from "../../core/routingHandler";
 const cfPropNameToHeaderName = {
   city: "x-open-next-city",
   country: "x-open-next-country",
-  region: "x-open-next-region",
+  regionCode: "x-open-next-region",
   latitude: "x-open-next-latitude",
   longitude: "x-open-next-longitude",
 };