[lib] Rip useShouldShowDisconnectedBar and useDisconnectedBar out of hooks/disconnected-bar
Summary:
These hooks are no longer relevant since DisconnectedBar is now about displaying information about network connectivity, not keyserver connectivity.
Depends on D10475
Test Plan: These functions are no longer used.
Reviewers: ashoat, ginsu, tomek
Reviewed By: ashoat
Subscribers: inka
Differential Revision: https://phab.comm.dev/D10476