Fix comments in Status (#8429)

Summary:
Signed-off-by: lorinlee <lorinlee1996@gmail.com>

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8429

Reviewed By: zhichao-cao

Differential Revision: D29256538

Pulled By: ajkr

fbshipit-source-id: fa483861148d82119f4c8775d0cf5f6c71b06215

include/rocksdb/status.h

@@ -452,10 +452,8 @@ class Status {
 
  protected:
   // A nullptr state_ (which is always the case for OK) means the message
-  // is empty.
-  // of the following form:
-  //    state_[0..3] == length of message
-  //    state_[4..]  == message
+  // is empty, else state_ points to message.
+
   Code code_;
   SubCode subcode_;
   Severity sev_;