[lib] Fix updatesCurrentAsOf returned from siweAuth

Summary: siweAuth returns LogInResult where updatesCurrentAsOf is of type {+[keyserverID: string]: number}. response.serverTime is a number. Flow didn't catch this because to it response is any. We use ashoatKeyserverID because this action was not yet refactored to work with multiple keyservers.

Test Plan: Checked that the types are now correct

Reviewers: kamil, michal, ginsu, ashoat

Reviewed By: ashoat

Subscribers: varun, ashoat, tomek

Differential Revision: https://phab.comm.dev/D10190