Bump prometheus_exporter from 2.1.0 to 2.1.1 (#611)

Bumps [prometheus_exporter](https://github.com/discourse/prometheus_exporter) from 2.1.0 to 2.1.1.
- [Release notes](https://github.com/discourse/prometheus_exporter/releases)
- [Changelog](https://github.com/discourse/prometheus_exporter/blob/main/CHANGELOG)
- [Commits](discourse/prometheus_exporter@v2.1.0...v2.1.1)

---
updated-dependencies:
- dependency-name: prometheus_exporter
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Gemfile.lock

@@ -210,7 +210,7 @@ GEM
     parser (3.3.2.0)
       ast (~> 2.4.1)
       racc
-    prometheus_exporter (2.1.0)
+    prometheus_exporter (2.1.1)
       webrick
     pry (0.14.2)
       coderay (~> 1.1)