Didn't really work to fix these tests due to the sticky nature of the
failure. Also I can no longer reproduce locally, so the hope is that
these are fixed by https://github.com/ppy/osu/pull/30634.
After switching `UserLookupCache` to `GET /users/lookup` from `GET
/users`, multiplayer sort of breaks, since the former endpoint does not
return `ruleset_statistics`, which are used in multiplayer to show
users' ranks. Therefore, switch multiplayer to use the appropriate
request type directly.