Update nyholm/psr7 requirement from ^1.3 to ^1.4

Updates the requirements on [nyholm/psr7](https://github.com/Nyholm/psr7) to permit the latest version.
- [Release notes](https://github.com/Nyholm/psr7/releases)
- [Changelog](https://github.com/Nyholm/psr7/blob/master/CHANGELOG.md)
- [Commits](Nyholm/psr7@1.3.0...1.4.0)

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

composer.json

@@ -59,7 +59,7 @@
         "guzzlehttp/psr7": "^1.7",
         "http-interop/http-factory-guzzle": "^1.0",
         "laminas/laminas-diactoros": "^2.4",
-        "nyholm/psr7": "^1.3",
+        "nyholm/psr7": "^1.4",
         "nyholm/psr7-server": "^1.0.1",
         "phpspec/prophecy": "^1.12",
         "phpstan/phpstan": "^0.12.80",