Blob DB: remove unreacheable code

Summary:
Fixing #3604.
Closes https://github.com/facebook/rocksdb/pull/3606

Reviewed By: siying

Differential Revision: D7276604

Pulled By: yiwu-arbug

fbshipit-source-id: 915c5897b010d28956f369989e49e64785d1161f

utilities/blob_db/blob_db_iterator.h

@@ -129,7 +129,6 @@ class BlobDBIterator : public Iterator {
         }
         return false;
       }
-      return status_.IsNotFound();
     } else {
       return false;
     }