- Revert 'Have [MSC4186: Simplified Sliding Sync](https://github.com/matrix-org/matrix-spec-proposals/pull/4186) return a new response immediately if a room subscription has changed and produced a new response. ([\#19714](https://github.com/element-hq/synapse/issues/19714))' (introduced in 1.153.0rc1) due to performance problems. ([\#19784](https://github.com/element-hq/synapse/issues/19784))