Update release history 6.14 (#7525)

Summary:
Update release history for 6.14

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7525

Test Plan: No code change

Reviewed By: jay-zhuang

Differential Revision: D24224690

Pulled By: akankshamahajan15

fbshipit-source-id: 95441aefde96672fea5a6af5d7e67cdafb1ebdd2

HISTORY.md

 # Rocksdb Change Log
-## Unreleased
+## 6.14 (10/09/2020)
 ### Bug fixes
 * Fixed a bug after a `CompactRange()` with `CompactRangeOptions::change_level` set fails due to a conflict in the level change step, which caused all subsequent calls to `CompactRange()` with `CompactRangeOptions::change_level` set to incorrectly fail with a `Status::NotSupported("another thread is refitting")` error.
 * Fixed a bug that the bottom most level compaction could still be a trivial move even if `BottommostLevelCompaction.kForce` or `kForceOptimized` is set.

include/rocksdb/version.h

@@ -5,7 +5,7 @@
 #pragma once
 
 #define ROCKSDB_MAJOR 6
-#define ROCKSDB_MINOR 13
+#define ROCKSDB_MINOR 14
 #define ROCKSDB_PATCH 0
 
 // Do not use these. We made the mistake of declaring macros starting with