[lib] Use useUsersSupportThickThreads() (with auxUserInfos) in useUpdateRelationships()

Summary: https://linear.app/comm/issue/ENG-9509/accepting-a-friend-request-on-web-creates-thin-thread

Test Plan:

1. Mobile user makes a new thick thread with web user (with new message button)
2. Mobile user sends friend request
3. Throw some error in fetchUserIdentitiesPromise() so that finding user indentity always fails
4. Web user accepts the request
5. Before a new thin thread was created. Now no new threads are created, users are friends, because user identity is found in auxUserInfo.

Reviewers: kamil, tomek

Reviewed By: kamil

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D13938