Update HISTORY.md and version.h 6.22 release (#8427)

Summary: Pull Request resolved: https://github.com/facebook/rocksdb/pull/8427

Reviewed By: zhichao-cao

Differential Revision: D29246916

Pulled By: ajkr

fbshipit-source-id: ccd44ca1a6dd5101dc37f19b8e1fe6c0e3883e0a

HISTORY.md

@@ -1,5 +1,5 @@
 # Rocksdb Change Log
-## Unreleased
+## 6.22.0 (2021-06-18)
 ### Behavior Changes
 * Added two additional tickers, MEMTABLE_PAYLOAD_BYTES_AT_FLUSH and MEMTABLE_GARBAGE_BYTES_AT_FLUSH. These stats can be used to estimate the ratio of "garbage" (outdated) bytes in the memtable that are discarded at flush time.
 * Added API comments clarifying safe usage of Disable/EnableManualCompaction and EventListener callbacks for compaction.

include/rocksdb/version.h

@@ -10,7 +10,7 @@
 #include "rocksdb/rocksdb_namespace.h"
 
 #define ROCKSDB_MAJOR 6
-#define ROCKSDB_MINOR 21
+#define ROCKSDB_MINOR 22
 #define ROCKSDB_PATCH 0
 
 // Do not use these. We made the mistake of declaring macros starting with