build(deps): update psr/http-message requirement from ^1.0 to ^2.0

Updates the requirements on [psr/http-message](https://github.com/php-fig/http-message) to permit the latest version.
- [Release notes](https://github.com/php-fig/http-message/releases)
- [Changelog](https://github.com/php-fig/http-message/blob/master/CHANGELOG.md)
- [Commits](php-fig/http-message@1.0...2.0)

---
updated-dependencies:
- dependency-name: psr/http-message
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

composer.json

@@ -21,7 +21,7 @@
         "php-http/discovery": "^1.19",
         "psr/http-client": "^1.0",
         "psr/http-factory": "^1.0",
-        "psr/http-message": "^1.0",
+        "psr/http-message": "^2.0",
         "psr/http-server-handler": "^1.0"
     },
     "require-dev": {