Mention in HISTORY.md the fix in #10705 (#10720)

Summary:
Mention in HISTORY.md the fix in https://github.com/facebook/rocksdb/issues/10705.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/10720

Reviewed By: riversand963

Differential Revision: D39709455

Pulled By: cbi42

fbshipit-source-id: 1a2c9dd8425c73f7095ddb1d0b1cca8ed35b7ef2

HISTORY.md

@@ -2,6 +2,7 @@
 ## Unreleased
 ### Bug Fixes
 * Fix a bug in io_uring_prep_cancel in AbortIO API for posix which expects sqe->addr to match with read request submitted and wrong paramter was being passed.
+* Fixed a regression in iterator performance when the entire DB is a single memtable introduced in #10449. The fix is in #10705 and #10716.
 
 ## 7.7.0 (09/18/2022)
 ### Bug Fixes