[lib] Avoid useless updateRelationships call when logged out in handleFarcasterMutuals

Summary: This addresses ENG-9229.

Test Plan: We use a similar strategy here, which has been tested. This change is safe because it's simple and is using an approach I've tested before

Reviewers: will, varun

Reviewed By: varun

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D13298