[lib] Refactor keyserver reducer pt.2 - early return

Summary:
issue: https://linear.app/comm/issue/ENG-5350/refactor-reducekeyserverstore
Now that the reducers this reducer used to call got inlined, we can early return from the keyserver reducer

Test Plan: Tested a couple of actions: queueActivityUpdatesActionType, updateDisconnectedBarActionType, updateActivityActionTypes.success, updateConnectionStatusActionType, checked that they work as expected

Reviewers: michal, kamil, ginsu

Reviewed By: michal

Subscribers: ashoat, tomek, wyilio

Differential Revision: https://phab.comm.dev/D9820