Bump version

Update version to 6.28.2

Summary: Update version to 6.28.2 for bug fix

RocksDB 6.27.3

Improve HISTORY.md

RocksDB 6.26.0

update HISTORY.md and version.h for 6.25.3

Tag v6.25.1

Tag v6.24.2

Tag v6.23.3

Tag v6.23.2