Update symfony/messenger requirement from ^5.4 to ^6.0

Updates the requirements on [symfony/messenger](https://github.com/symfony/messenger) to permit the latest version.
- [Release notes](https://github.com/symfony/messenger/releases)
- [Changelog](https://github.com/symfony/messenger/blob/6.3/CHANGELOG.md)
- [Commits](symfony/messenger@v5.4.0...v6.0.19)

---
updated-dependencies:
- dependency-name: symfony/messenger
  dependency-type: direct:production
...

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

composer.json

@@ -36,7 +36,7 @@
     "doctrine/orm": "^2.9",
     "sensio/framework-extra-bundle": "^6.1",
     "symfony/console": "^5.4",
-    "symfony/messenger": "^5.4",
+    "symfony/messenger": "^6.0",
     "symfony/doctrine-messenger": "^5.4",
     "symfony/filesystem": "^5.4",
     "symfony/flex": "^1.3.1",