Build(deps): Bump message_bus from 3.3.8 to 3.4.0 (#15432)

Bumps [message_bus](https://github.com/discourse/message_bus) from 3.3.8 to 3.4.0.
- [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/v3.3.8...v3.4.0)

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

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

Gemfile.lock

@@ -223,7 +223,7 @@ GEM
     lz4-ruby (0.3.3)
     maxminddb (0.1.22)
     memory_profiler (1.0.0)
-    message_bus (3.3.8)
+    message_bus (3.4.0)
       rack (>= 1.1.3)
     method_source (1.0.0)
     mini_mime (1.1.2)