message: op-node: ComputeL2OutputRoot cleanup
  Cleans up the implementation of the `ComputeL2OutputRoot`
  function. No need for the intermediate `bytes.Buffer`.
diff: package rollup
  import (
  - "bytes"
  -
  "github.com/ethereum-optimism/optimism/op-node/eth"
  "github.com/ethereum/go-ethereum/common"
  "github.com/ethereum/go-ethereum/crypto"
  )
  func ComputeL2OutputRoot(l2OutputRootVersion eth.Bytes32, blockHash common.Hash, blockRoot common.Hash, storageRoot common.Hash) eth.Bytes32 {
  - var buf bytes.Buffer
  - buf.Write(l2OutputRootVersion[:])
  - buf.Write(blockRoot.Bytes())
  - buf.Write(storageRoot[:])
  - buf.Write(blockHash.Bytes())
  - return eth.Bytes32(crypto.Keccak256Hash(buf.Bytes()))
  + digest := crypto.Keccak256Hash(
  + l2OutputRootVersion[:],
  + blockRoot.Bytes(),
  + storageRoot[:],
  + blockHash.Bytes(),
  + )
  + return eth.Bytes32(digest)
  }
  