HISTORY.md update for bzip upgrade (#6767)

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

Reviewed By: riversand963

Differential Revision: D21283307

Pulled By: pdillinger

fbshipit-source-id: 8463bec725669d13846c728ad4b5bde43f9a84f8

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.
+
 ## 6.9.2 (04/16/2020)
 ### Public API Change
 * Add NewFileChecksumGenCrc32cFactory to the file checksum public API, such that the builtin Crc32c based file checksum generator factory can be used by applications.