[chore(cargo)](deps): Bump metrics-exporter-prometheus

Bumps [metrics-exporter-prometheus](https://github.com/metrics-rs/metrics) from 0.12.2 to 0.15.1.
- [Changelog](https://github.com/metrics-rs/metrics/blob/main/release.toml)
- [Commits](metrics-rs/metrics@metrics-exporter-prometheus-v0.12.2...metrics-exporter-prometheus-v0.15.1)

---
updated-dependencies:
- dependency-name: metrics-exporter-prometheus
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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