remove a note about raftstore.sync-log (#6563) (#6566)

tune-tikv-thread-performance.md

@@ -54,7 +54,7 @@ Starting from TiKV v5.0, all read requests use the unified thread pool for queri
 
 * The Raftstore thread pool.
 
-    The Raftstore thread pool is the most complex thread pool in TiKV. The default size (configured by `raftstore.store-pool-size`) is `2`. All write requests are written into RocksDB in the way of `fsync` from the Raftstore thread, unless you manually set `raftstore.sync-log` to `false`. Setting `raftstore.sync-log` to `false` improves write performance to a certain degree, but increases the risk of data loss in the case of machine failure).
+    The Raftstore thread pool is the most complex thread pool in TiKV. The default size (configured by `raftstore.store-pool-size`) is `2`. All write requests are written into RocksDB in the way of `fsync` from the Raftstore thread.
 
     Due to I/O, Raftstore threads cannot reach 100% CPU usage theoretically. To reduce disk writes as much as possible, you can put together multiple write requests and write them to RocksDB. It is recommended to keep the overall CPU usage below 60% (If the default number of threads is `2`, it is recommended to keep `TiKV-Details.Thread CPU.Raft store CPU` on Grafana within 120%). Do not increase the size of the Raftstore thread pool to improve write performance without thinking, because this might increase the disk burden and degrade performance.