Bump @octokit/request-error and @octokit/rest in /.buildkite

Bumps [@octokit/request-error](https://github.com/octokit/request-error.js) to 6.1.7 and updates ancestor dependency [@octokit/rest](https://github.com/octokit/rest.js). These dependencies need to be updated together.


Updates `@octokit/request-error` from 2.1.0 to 6.1.7
- [Release notes](https://github.com/octokit/request-error.js/releases)
- [Commits](octokit/request-error.js@v2.1.0...v6.1.7)

Updates `@octokit/rest` from 18.12.0 to 21.1.0
- [Release notes](https://github.com/octokit/rest.js/releases)
- [Commits](octokit/rest.js@v18.12.0...v21.1.0)

---
updated-dependencies:
- dependency-name: "@octokit/request-error"
  dependency-type: indirect
- dependency-name: "@octokit/rest"
  dependency-type: direct:production
...

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