Bump ethereumjs-util from 6.2.0 to 7.0.0 (#2222)

* Bump ethereumjs-util from 6.2.0 to 7.0.0

Bumps [ethereumjs-util](https://github.com/ethereumjs/ethereumjs-util) from 6.2.0 to 7.0.0.
- [Release notes](https://github.com/ethereumjs/ethereumjs-util/releases)
- [Changelog](https://github.com/ethereumjs/ethereumjs-util/blob/master/CHANGELOG.md)
- [Commits](ethereumjs/ethereumjs-util@v6.2.0...v7.0.0)

Signed-off-by: dependabot-preview[bot] <[email protected]>

* update use of ethereumjs-util

* fix use of keccak hash function

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>
Co-authored-by: Francisco Giordano <[email protected]>