build(deps): Bump actix-web-prom from 0.2.0 to 0.5.1

Bumps [actix-web-prom](https://github.com/nlopes/actix-web-prom) from 0.2.0 to 0.5.1.
- [Release notes](https://github.com/nlopes/actix-web-prom/releases)
- [Commits](https://github.com/nlopes/actix-web-prom/commits)

---
updated-dependencies:
- dependency-name: actix-web-prom
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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