Update openai-php/client version to 0.18 (#38)

Author: annuh

composer.json

@@ -17,7 +17,7 @@
     "require": {
         "php": "^8.2.0",
         "nyholm/psr7": "^1.8.2",
-        "openai-php/client": "^0.17.0",
+        "openai-php/client": "^0.18.0",
         "psr/http-client": "^1.0.3",
         "psr/http-factory": "^1.1.0",
         "symfony/config": "^6.4|^7.3|^8.0",