Bump @metamask/eth-sig-util from 5.0.0 to 7.0.2 in /webapp

Bumps [@metamask/eth-sig-util](https://github.com/MetaMask/eth-sig-util) from 5.0.0 to 7.0.2.
- [Release notes](https://github.com/MetaMask/eth-sig-util/releases)
- [Changelog](https://github.com/MetaMask/eth-sig-util/blob/main/CHANGELOG.md)
- [Commits](MetaMask/eth-sig-util@v5.0.0...v7.0.2)

---
updated-dependencies:
- dependency-name: "@metamask/eth-sig-util"
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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