docs: fix broken link (#8746)

Author: benmccann

sites/svelte.dev/README.md

@@ -4,7 +4,7 @@ A local database is only required in dev mode if you want to test reading and wr
 
 Note also that in dev mode, the REPL will currently only work in Chrome, [as noted in the Vite documentation](https://vitejs.dev/guide/features.html#web-workers), pending support in Firefox for `import` statements in web workers.
 
-If you do want to use a database, set it up on [Supabase](https://supabase.com) with the instructions [here](../../db) and set the corresponding environment variables.
+If you do want to use a database, set it up on [Supabase](https://supabase.com) with the instructions [here](https://github.com/sveltejs/sites/tree/master/db) and set the corresponding environment variables.
 
 Run the site sub-project: