Update slim/http requirement from ^1.3 to ^1.4

Updates the requirements on [slim/http](https://github.com/slimphp/Slim-Http) to permit the latest version.
- [Release notes](https://github.com/slimphp/Slim-Http/releases)
- [Commits](slimphp/Slim-Http@1.3...1.4.0)

---
updated-dependencies:
- dependency-name: slim/http
  dependency-version: 1.4.0
  dependency-type: direct:development
...

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

Author: dependabot[bot]

composer.json

@@ -66,7 +66,7 @@
         "phpspec/prophecy-phpunit": "^2.1",
         "phpstan/phpstan": "^1 || ^2",
         "phpunit/phpunit": "^9.6 || ^10 || ^11 || ^12",
-        "slim/http": "^1.3",
+        "slim/http": "^1.4",
         "slim/psr7": "^1.6",
         "squizlabs/php_codesniffer": "^3.10",
         "vimeo/psalm": "^5 || ^6"