message: root: Update CHANGELOG for utils assertDefinedAndNotNull change
diff: - @cosmjs/tendermint-rpc: Remove types `BlockHash`, `TxBytes` and `TxHash`. Use
  `Uint8Array` instead.
  +### Added
  +
  +- @cosmjs/utils: Added `assertDefinedAndNotNull`.
  +
  +### Removed
  +
  +- @cosmjs/utils: `assertDefined` removed in favour of `assertDefinedAndNotNull`.
  +
  ## 0.23.2 (2021-01-06)
  ### Security
  