Bump prom-client from 15.1.0 to 15.1.2 in /orchestrator

Bumps [prom-client](https://github.com/siimon/prom-client) from 15.1.0 to 15.1.2.
- [Release notes](https://github.com/siimon/prom-client/releases)
- [Changelog](https://github.com/siimon/prom-client/blob/master/CHANGELOG.md)
- [Commits](siimon/prom-client@v15.1.0...v15.1.2)

---
updated-dependencies:
- dependency-name: prom-client
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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