Fix incorrect order of comments in win_thread.cc (#9033)

Summary:
The comments in the `#endif` section at the end of the file were in the
wrong order.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/9033

Reviewed By: mrambacher

Differential Revision: D31935856

Pulled By: ajkr

fbshipit-source-id: 24aca039993d6e27022cfe8d6434e90f2934c87c

port/win/win_thread.cc

@@ -185,5 +185,5 @@ unsigned int __stdcall  WindowsThread::Data::ThreadProc(void* arg) {
 } // namespace port
 }  // namespace ROCKSDB_NAMESPACE
 
-#endif  // OS_WIN
 #endif  // !_POSIX_THREADS
+#endif  // OS_WIN