Update psr/http-message requirement from ^1.0 to ^1.1

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...1.1)

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

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

composer.json

@@ -48,7 +48,7 @@
         "nikic/fast-route": "^1.3",
         "psr/container": "^1.0 || ^2.0",
         "psr/http-factory": "^1.0",
-        "psr/http-message": "^1.0",
+        "psr/http-message": "^1.1",
         "psr/http-server-handler": "^1.0",
         "psr/http-server-middleware": "^1.0",
         "psr/log": "^1.1 || ^2.0 || ^3.0"