[keyserver][lib][native][web] Remove connection field from redux

Summary:
issue: https://linear.app/comm/issue/ENG-4460/refactor-connection-field
This diff is the same as D8932, but this time we don't need a migration because connection is not being persisted. This diff does make it temporarily be presisted, becuse all of
keyserverStore is being persisted. I will fix this in the next diff

Test Plan: ran yarn flow-all.

Reviewers: michal, kamil

Reviewed By: michal

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D9023