HISTORY.md update for bzip upgrade (facebook#6767)

Summary:
See facebook#6714 and facebook#6703
Pull Request resolved: facebook#6767

Reviewed By: riversand963

Differential Revision: D21283307

Pulled By: pdillinger

fbshipit-source-id: 8463bec725669d13846c728ad4b5bde43f9a84f8

Author: pdillinger

HISTORY.md

@@ -1,4 +1,8 @@
 # Rocksdb Change Log
+## Unreleased
+### Bug Fixes
+* Upgraded version of bzip library (1.0.6 -> 1.0.8) used with RocksJava to address potential vulnerabilities if an attacker can manipulate compressed data saved and loaded by RocksDB (not normal). See issue #6703.
+
 ## 6.8.1 (03/30/2020)
 ### Behavior changes
 * Since RocksDB 6.8.0, ttl-based FIFO compaction can drop a file whose oldest key becomes older than options.ttl while others have not. This fix reverts this and makes ttl-based FIFO compaction use the file's flush time as the criterion. This fix also requires that max_open_files = -1 and compaction_options_fifo.allow_compaction = false to function properly.