Reflect out-of-band leaves in MSC4222 state_after on sync

[ara4n]

Out-of-band membership events are outliers which never enter the current state delta stream.

Clients using MSC4222's state_after do not apply timeline events to state, so without this they never learn that an invite rejection or knock rescission changed their membership, and e.g. Element Web keeps showing a knock as pending after rescinding it.

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