ticdc: add scheduler.region-count-per-span in v8.5.4 release notes

releases/release-8.5.4.md

@@ -86,6 +86,7 @@ Newly created v8.5.3 clusters can be smoothly upgraded to v8.5.4. However, v8.5.
 | TiKV | <ul><li>[`region-compact-check-interval`](https://docs.pingcap.com/tidb/v8.5/tikv-configuration-file#region-compact-check-interval)</li><li>[`region-compact-check-step`](https://docs.pingcap.com/tidb/v8.5/tikv-configuration-file#region-compact-check-step)</li><li>[`region-compact-min-tombstones`](https://docs.pingcap.com/tidb/v8.5/tikv-configuration-file#region-compact-min-tombstones)</li><li>[`region-compact-tombstones-percent`](https://docs.pingcap.com/tidb/v8.5/tikv-configuration-file#region-compact-tombstones-percent)</li><li>[`region-compact-min-redundant-rows`](https://docs.pingcap.com/tidb/v8.5/tikv-configuration-file#region-compact-min-redundant-rows-new-in-v710)</li><li>[`region-compact-redundant-rows-percent`](https://docs.pingcap.com/tidb/v8.5/tikv-configuration-file#region-compact-redundant-rows-percent-new-in-v710)</li></ul> | Deprecated | These configuration items are replaced by the [`gc.auto-compaction`](https://docs.pingcap.com/tidb/v8.5/tikv-configuration-file#gcauto-compaction) configuration group, which controls the automatic compaction behavior. [#18727](https://github.com/tikv/tikv/issues/18727) [@v01dstar](https://github.com/v01dstar) |
 | TiKV | [`gc.auto-compaction`](https://docs.pingcap.com/tidb/v8.5/tikv-configuration-file#gcauto-compaction) configuration group: <ul><li>[`gc.auto-compaction.check-interval`](https://docs.pingcap.com/tidb/v8.5/tikv-configuration-file#check-interval-new-in-v757-and-v854)</li><li>[`gc.auto-compaction.tombstone-num-threshold`](https://docs.pingcap.com/tidb/v8.5/tikv-configuration-file#tombstone-num-threshold-new-in-v757-and-v854)</li><li>[`gc.auto-compaction.tombstone-percent-threshold`](https://docs.pingcap.com/tidb/v8.5/tikv-configuration-file#tombstone-percent-threshold-new-in-v757-and-v854)</li><li>[`gc.auto-compaction.redundant-rows-threshold`](https://docs.pingcap.com/tidb/v8.5/tikv-configuration-file#redundant-rows-threshold-new-in-v757-and-v854)</li><li>[`gc.auto-compaction.redundant-rows-percent-threshold`](https://docs.pingcap.com/tidb/v8.5/tikv-configuration-file#redundant-rows-percent-threshold-new-in-v757-and-v854)</li><li>[`gc.auto-compaction.bottommost-level-force`](https://docs.pingcap.com/tidb/v8.5/tikv-configuration-file#bottommost-level-force-new-in-v757-and-v854) </li></ul>| Newly added | This configuration group controls the automatic compaction behavior. [#18727](https://github.com/tikv/tikv/issues/18727) [@v01dstar](https://github.com/v01dstar) |
 | TiFlash | [`flash.graceful_wait_shutdown_timeout`](https://docs.pingcap.com/tidb/v8.5/tiflash-configuration#graceful_wait_shutdown_timeout-new-in-v854) | Newly added | Controls the maximum wait time (in seconds) for a graceful TiFlash shutdown. The default value is `600`. When shutting down TiFlash, it continues executing unfinished MPP tasks but no longer accepts new MPP tasks. If all MPP tasks finish before the timeout, TiFlash shuts down immediately; otherwise, it is forcibly shut down after the timeout expires. [#10266](https://github.com/pingcap/tiflash/issues/10266) [@gengliqi](https://github.com/gengliqi) |
+| TiCDC | [`scheduler.region-count-per-span`](https://docs.pingcap.com/tidb/v8.5/ticdc-changefeed-config#region-count-per-span-new-in-v854) | Newly added | Introduced in the [TiCDC new architecture](https://docs.pingcap.com/tidb/v8.5/ticdc-architecture). During changefeed initialization, TiCDC splits tables that meet the split conditions according to this parameter. Each split sub-table contains at most `region-count-per-span` Regions. The default value is `100`. |
 
 ### MySQL compatibility