Bump aws-partitions from 1.338.0 to 1.618.0

Bumps [aws-partitions](https://github.com/aws/aws-sdk-ruby) from 1.338.0 to 1.618.0.
- [Release notes](https://github.com/aws/aws-sdk-ruby/releases)
- [Changelog](https://github.com/aws/aws-sdk-ruby/blob/version-3/gems/aws-partitions/CHANGELOG.md)
- [Commits](https://github.com/aws/aws-sdk-ruby/commits

)

---
updated-dependencies:
- dependency-name: aws-partitions
  dependency-type: indirect
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>