Clarify compiler support release note (#9593)

Summary:
in HISTORY.md

Pull Request resolved: #9593

Test Plan: release note only

Reviewed By: siying

Differential Revision: D34318189

Pulled By: pdillinger

fbshipit-source-id: ba2eca8bede2d42a3fefd10b954b92cb54f831f2

HISTORY.md

@@ -12,7 +12,7 @@
 * DisableManualCompaction() doesn't have to wait scheduled manual compaction to be executed in thread-pool to cancel the job.
 
 ### Public API changes
-* Require C++17 compatible compiler (GCC >= 7, Clang >= 5, Visual Studio >= 2017). See #9388.
+* Require C++17 compatible compiler (GCC >= 7, Clang >= 5, Visual Studio >= 2017) for compiling RocksDB and any code using RocksDB headers. See #9388.
 * Added `ReadOptions::rate_limiter_priority`. When set to something other than `Env::IO_TOTAL`, the internal rate limiter (`DBOptions::rate_limiter`) will be charged at the specified priority for file reads associated with the API to which the `ReadOptions` was provided.
 * Remove HDFS support from main repo.
 * Remove librados support from main repo.