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] <[email protected]>

composer.json

@@ -38,7 +38,7 @@
         "ext-json": "*",
         "ext-libxml": "*",
         "psr/http-factory": "^1.0",
-        "psr/http-message": "^1.0"
+        "psr/http-message": "^1.1"
     },
     "require-dev": {
         "adriansuter/php-autoload-override": "^1.4",