Upgrade: Bump prometheus-client from 0.17.1 to 0.18.0

Bumps [prometheus-client](https://github.com/prometheus/client_python) from 0.17.1 to 0.18.0.
- [Release notes](https://github.com/prometheus/client_python/releases)
- [Commits](prometheus/client_python@v0.17.1...v0.18.0)

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

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

requirements.txt

@@ -13,7 +13,7 @@ multidict==6.0.4
 openttd-helpers==1.4.0
 openttd-protocol==1.6.1
 pproxy==2.7.8
-prometheus-client==0.17.1
+prometheus-client==0.18.0
 sentry-sdk==1.30.0
 typing_extensions==4.7.1
 urllib3==2.0.4