[pip](deps): Bump prometheus-client from 0.20.0 to 0.21.0 (#202)

Bumps [prometheus-client](https://github.com/prometheus/client_python) from 0.20.0 to 0.21.0.
- [Release notes](https://github.com/prometheus/client_python/releases)
- [Commits](prometheus/client_python@v0.20.0...v0.21.0)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

poetry.lock

@@ -23,7 +23,7 @@ jishaku = "^2.5.2"
 pyyaml = "^6.0.2"
 watchfiles = "^0.24.0"
 typing-extensions = "^4.12.2"
-prometheus-client = "^0.20.0"
+prometheus-client = "^0.21.0"
 prometheus-async = "^22.2.0"
 parsedatetime = "^2.6"
 humanize = "^4.10.0"