[web] Update InitialReduxStateGate to remove reference to LegacyRawThreadInfo

Summary:
I think @atul missed this one in one of his refactors, and Flow didn't catch it for some reason.

We should not be seeing LegacyRawThreadInfo here in the modern web client, as keyserver should not be sending it to the modern web client.

Depends on D12491

Test Plan: Flow

Reviewers: kamil, marcin, atul

Reviewed By: kamil

Subscribers: tomek, atul

Differential Revision: https://phab.comm.dev/D12492