Edge functions: invoking an invalid x-region re-routes to an available region

# Bug - [x] I confirm this is a bug with Supabase, not with my own application. - [x] I confirm I have searched the [Docs](https://docs.supabase.com), GitHub [Discussions](https://github.com/supabase/supabase/discussions), and [Discord](https://discord.supabase.com). ## Describe the bug Using regional invocation does not strictly force the selected region and re-routes to an available region. This bug affects the capability to simulate a regional outage. ## To Reproduce Steps to reproduce the behavior, please provide code snippets or a repository: 1. Set --header 'x-region: invalid-region' 2. Check metadata from edge function logs 3. It connects to an available server ## Expected behavior It should return an appropriate error status. Taken from the documentation (https://supabase.com/docs/guides/functions/regional-invocation): “If you explicitly specify the region via x-region header, requests will NOT be automatically re-routed to another region and you should consider temporarily changing regions during the outage.”