Swap FK group_wiki_repository_states.group_id to namespaces.id for LFK

Summary

As part of our "sharding key" efforts we need to mark the group_wiki_repository_states table as exempt from sharding in !182030 (comment 2356809867), but it has foreign key references. The table with foreign key references is: namespaces. We are going to replace the foreign keys with "loose foreign keys".