Update webmozart/assert requirement from ^1.9 to ^2.1

Updates the requirements on [webmozart/assert](https://github.com/webmozarts/assert) to permit the latest version.
- [Release notes](https://github.com/webmozarts/assert/releases)
- [Changelog](https://github.com/webmozarts/assert/blob/master/CHANGELOG.md)
- [Commits](webmozarts/assert@1.9.0...2.1.2)

---
updated-dependencies:
- dependency-name: webmozart/assert
  dependency-version: 2.1.2
  dependency-type: direct:production
...

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

Author: dependabot[bot]

composer.json

@@ -31,7 +31,7 @@
         "symfony/framework-bundle": "^6.4 || ^7.4",
         "symfony/http-kernel": "^6.4 || ^7.4",
         "twig/twig": "^3.3",
-        "webmozart/assert": "^1.9"
+        "webmozart/assert": "^2.1"
     },
     "replace": {
         "sylius/mailer": "self.version"