Build(deps): Bump message-bus-client in /app/assets/javascripts (#18944)

Bumps [message-bus-client](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-client
  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>

app/assets/javascripts/discourse/package.json

@@ -81,7 +81,7 @@
     "jsdom": "^20.0.2",
     "loader.js": "^4.7.0",
     "markdown-it": "^13.0.1",
-    "message-bus-client": "^4.2.0",
+    "message-bus-client": "^4.3.0",
     "messageformat": "0.1.5",
     "pretender": "^3.4.7",
     "pretty-text": "1.0.0",

app/assets/javascripts/yarn.lock

@@ -6868,10 +6868,10 @@ merge2@^1.2.3, merge2@^1.3.0:
   resolved "https://registry.yarnpkg.com/merge2/-/merge2-1.4.1.tgz#4368892f885e907455a6fd7dc55c0c9d404990ae"
   integrity sha512-8q7VEgMJW4J8tcfVPy8g09NcQwZdbwFEqhe/WZkoIzjn/3TGDwtOCYtXGxA3O8tPzpczCCDgv+P2P5y00ZJOOg==
 
-message-bus-client@^4.2.0:
-  version "4.2.0"
-  resolved "https://registry.yarnpkg.com/message-bus-client/-/message-bus-client-4.2.0.tgz#1b994a1309eaa3d5b1ebe6d0b2f911e3355c2314"
-  integrity sha512-m0aOFoZybxNjrILZdG6tkawMHdwxi5AysUusZSkl5AYbcFwxHhHVlmyBILzuMKNcR1oET3d5eKpFlgPAc9IjOQ==
+message-bus-client@^4.3.0:
+  version "4.3.0"
+  resolved "https://registry.yarnpkg.com/message-bus-client/-/message-bus-client-4.3.0.tgz#03710b9acdbaa4c9117b2215b2dd8038a360c168"
+  integrity sha512-tJbSFz+NB8fBXn5OqGqisi881SUv1ypIoETHgyQHfg5NHFr15Y+BIx4gPqXhy5iG0EJlayZfcNyFxYfFfhyv+w==
 
 messageformat@0.1.5:
   version "0.1.5"