message: contracts-bedrock: fix type
diff: @@ -4,7 +4,7 @@ import { task, types } from 'hardhat/config'
  import '@nomiclabs/hardhat-ethers'
  import 'hardhat-deploy'
  import { HardhatRuntimeEnvironment } from 'hardhat/types'
  -import { Contract, providers, Wallet, Signer } from 'ethers'
  +import { Contract, providers, Wallet, Signer, BigNumber } from 'ethers'
  import { predeploys } from '../src'
  @@ -162,6 +162,9 @@ const checkGenesisMagic = async (
  startingBlockNumber = hre.deployConfig.l2OutputOracleStartingBlockNumber
  }
  + // ensure that the starting block number is a number
  + startingBlockNumber = BigNumber.from(startingBlockNumber).toNumber()
  +
  const block = await l2Provider.getBlock(startingBlockNumber)
  const extradata = block.extraData
  