chore: remove old group references from CODEOWNERS (#47763)

This PR cleans up CODEOWNERS after the infrastructure teams have been
renamed.

Removes old group references:
- @supabase/infra → (removed, now @supabase/platform)


The new group names are now in use and working correctly.


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Chores**
* Updated ownership settings for one shared data area to reflect the
current team responsible for it.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

.github/CODEOWNERS

@@ -21,4 +21,4 @@
 /apps/studio/components/interfaces/Organization/Documents/          @supabase/security
 /apps/studio/pages/new/index.tsx                                    @supabase/security
 
-/packages/shared-data/compute-disk-limits.ts @supabase/infra @supabase/platform
+/packages/shared-data/compute-disk-limits.ts @supabase/platform