Update psr/http-message requirement from ^1.0.1 to ^1.0.1 || ^2.0 (#598)

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...2.0)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

composer.json

@@ -18,7 +18,7 @@
         "phpdocumentor/type-resolver": "^1.4",
         "psr/container": "^1.1 || ^2",
         "psr/http-factory": "^1",
-        "psr/http-message": "^1.0.1",
+        "psr/http-message": "^1.0.1 || ^2.0",
         "psr/http-server-handler": "^1",
         "psr/http-server-middleware": "^1",
         "psr/simple-cache": "^1.0.1 || ^2 || ^3",