chore: add backend team as an additional codeowner on orioledb

The intention was to allow PG team to also merge orioledb changes, not
to have all changes under orioledb image dir to be blocked on PG team.

Author: darora

.github/CODEOWNERS

@@ -1,4 +1,4 @@
 * @supabase/backend
 migrations/ @supabase/cli @supabase/backend
-docker/orioledb @supabase/postgres
+docker/orioledb @supabase/postgres @supabase/backend
 common.vars.pkr.hcl @supabase/postgres @supabase/backend