Bump ethnum from 1.5.0 to 1.5.2 in /rust-sdk/core

Bumps [ethnum](https://github.com/nlordell/ethnum-rs) from 1.5.0 to 1.5.2.
- [Release notes](https://github.com/nlordell/ethnum-rs/releases)
- [Commits](nlordell/ethnum-rs@v1.5.0...v1.5.2)

---
updated-dependencies:
- dependency-name: ethnum
  dependency-version: 1.5.2
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]