Update HISTORY for PR 9504 (#9513)

Summary: Pull Request resolved: https://github.com/facebook/rocksdb/pull/9513

Reviewed By: riversand963

Differential Revision: D34046181

Pulled By: ltamasi

fbshipit-source-id: a5d8d3bf84e5c13bdc6cbd5ba1b4216bad9adfc5

HISTORY.md

@@ -4,6 +4,9 @@
 * Fixed a major bug in which batched MultiGet could return old values for keys deleted by DeleteRange when memtable Bloom filter is enabled (memtable_prefix_bloom_size_ratio > 0). (The fix includes a substantial MultiGet performance improvement in the unusual case of both memtable_whole_key_filtering and prefix_extractor.)
 * Fixed more cases of EventListener::OnTableFileCreated called with OK status, file_size==0, and no SST file kept. Now the status is Aborted.
 
+### Performance Improvements
+* Mitigated the overhead of building the file location hash table used by the online LSM tree consistency checks, which can improve performance for certain workloads (see #9351).
+
 ### Public API changes
 * Require C++17 compatible compiler (GCC >= 7, Clang >= 5, Visual Studio >= 2017). See #9388.
 * Remove HDFS support from main repo.