Build(deps): Bump message_bus from 4.2.0 to 4.3.0 (#18922)

Bumps [message_bus](https://github.com/discourse/message_bus) from 4.2.0 to 4.3.0.
- [Release notes](https://github.com/discourse/message_bus/releases)
- [Changelog](https://github.com/discourse/message_bus/blob/main/CHANGELOG)
- [Commits](https://github.com/discourse/message_bus/compare/v4.2.0...v4.3.0)

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

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

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

Gemfile.lock

@@ -226,7 +226,7 @@ GEM
     matrix (0.4.2)
     maxminddb (0.1.22)
     memory_profiler (1.0.1)
-    message_bus (4.2.0)
+    message_bus (4.3.0)
       rack (>= 1.1.3)
     method_source (1.0.0)
     mini_mime (1.1.2)