message: update description to uncles
diff: @@ -236,7 +236,7 @@ More information about the Transaction of Nervos CKB can be found in [whitepaper
  | `txs_commit` | H256(hash) | **The Merkle Root of the Merkle trie with the hash of transactions as leaves.** |
  | `txs_proposal` | H256(hash) | **The Merkle Root of the Merkle trie with the hash of short transaction IDs as leaves.** |
  | `uncles_count` | uint32 | **The number of uncle blocks.** |
  -| `uncles_hash` | H256(hash) | **The Merkle Root of the Merkle trie with the hash of uncle blocks as leaves.** |
  +| `uncles_hash` | H256(hash) | **The hash of the serialized uncle blocks data.** This will later be changed to using Merle Trie as well. |
  | `version` | uint32 | **The version of the block**. This is for solving the compatibility issues might be occurred after a fork. |
  #### UncleBlock
  