update consensus vote rate from 2/3 to 1/2

[HarryLiIsMe]

• make sure that you have executed all the following process and no errors occur

  • [ ] make fmt
  • [ ] make lint
  • [ ] make test

• The major changes of this PR

• The major impacts of this PR

  • [ ] Impact WASM?
  • [ ] Impact Web3 API?
  • [ ] Impact mainnet data compatibility?

• Extra documentations