Add recent fixes to HISTORY.md (#7617)

Summary:
The recently reverted behavior changes were released to at least one
place internally, so we should mention the reverts in release notes.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7617

Reviewed By: akankshamahajan15

Differential Revision: D24654343

Pulled By: ajkr

fbshipit-source-id: eb64b2797d8508cd95a2dc2698122c1be29ce817

HISTORY.md

@@ -8,6 +8,8 @@
 * Since 6.14, fix a bug that could cause a stalled write to crash with mixed of slowdown and no_slowdown writes (`WriteOptions.no_slowdown=true`).
 * Fixed a bug which causes hang in closing DB when refit level is set in opt build. It was because ContinueBackgroundWork() was called in assert statement which is a no op. It was introduced in 6.14.
 * Perform post-flush updates of in-memory data structures of memtable list in a callback that will be called by the thread writing to MANIFEST file before signaling other threads and releasing db mutex.
+* Reverted a behavior change silently introduced in 6.14.2, in which the effects of the `ignore_unknown_options` flag (used in option parsing/loading functions) changed.
+* Reverted a behavior change silently introduced in 6.14, in which options parsing/loading functions began returning `NotFound` instead of `InvalidArgument` for option names not available in the present version.
 
 ### Public API Change
 * Deprecate `BlockBasedTableOptions::pin_l0_filter_and_index_blocks_in_cache` and `BlockBasedTableOptions::pin_top_level_index_and_filter`. These options still take effect until users migrate to the replacement APIs in `BlockBasedTableOptions::metadata_cache_options`. Migration guidance can be found in the API comments on the deprecated options.