Bump backoff from 0.2.1 to 0.4.0

Bumps [backoff](https://github.com/ihrwein/backoff) from 0.2.1 to 0.4.0.
- [Release notes](https://github.com/ihrwein/backoff/releases)
- [Commits](https://github.com/ihrwein/backoff/compare/v0.2.1...v0.4.0

)

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

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