deps(deps): update metrics-exporter-prometheus requirement

Updates the requirements on [metrics-exporter-prometheus](https://github.com/metrics-rs/metrics) to permit the latest version.
- [Changelog](https://github.com/metrics-rs/metrics/blob/main/release.toml)
- [Commits](metrics-rs/metrics@metrics-exporter-prometheus-v0.17.2...metrics-exporter-prometheus-v0.18.0)

---
updated-dependencies:
- dependency-name: metrics-exporter-prometheus
  dependency-version: 0.18.0
  dependency-type: direct:production
...

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

Author: dependabot[bot]

Cargo.toml

@@ -38,7 +38,7 @@ serde_yaml = "0.9"
 
 # Tracing and observability
 metrics = "0.24"
-metrics-exporter-prometheus = "0.17.2"
+metrics-exporter-prometheus = "0.18.0"
 opentelemetry = "0.31.0"
 opentelemetry-otlp = { version = "0.31.0", features = ["grpc-tonic", "trace"] }
 opentelemetry_sdk = { version = "0.31.0", features = ["rt-tokio"] }