Bump either from 1.8.1 to 1.9.0 in /deepwell

Bumps [either](https://github.com/bluss/either) from 1.8.1 to 1.9.0.
- [Commits](rayon-rs/either@1.8.1...1.9.0)

---
updated-dependencies:
- dependency-name: either
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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