This triggers the client to start a new sliding sync connection. If we
don't do this and the client asks for the full range of rooms, we end up
sending down all rooms and their state from scratch (which can be very
slow)
This causes things like
https://github.com/element-hq/element-x-ios/issues/3115 after we restart
the server
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Co-authored-by: Eric Eastwood <eric.eastwood@beta.gouv.fr>
