Call out a bug in HISTORY (#7690)

Summary:
It's worth mentioning the corner case bug fixed in PR 7621.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7690

Test Plan: N/A

Reviewed By: zhichao-cao

Differential Revision: D25056678

Pulled By: cheng-chang

fbshipit-source-id: 1ab42ec080f3ffe21f5d97acf65ee0af993112ba

HISTORY.md

@@ -21,6 +21,7 @@
 * Fixed a potential bug caused by evaluating `TableBuilder::NeedCompact()` before `TableBuilder::Finish()` in compaction job. For example, the `NeedCompact()` method of `CompactOnDeletionCollector` returned by built-in `CompactOnDeletionCollectorFactory` requires `BlockBasedTable::Finish()` to return the correct result. The bug can cause a compaction-generated file not to be marked for future compaction based on deletion ratio.
 * Fixed a seek issue with prefix extractor and timestamp.
 * Fixed a bug of encoding and parsing BlockBasedTableOptions::read_amp_bytes_per_bit as a 64-bit integer.
+* Fixed a bug of a recovery corner case, details in PR7621.
 
 ### 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.