docs: Correct OpenAI API link in README.md from broken beta subdomain (#141)

Author: megoxv

README.md

@@ -8,7 +8,7 @@
 </p>
 
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-**OpenAI PHP** for Laravel is a community-maintained PHP API client that allows you to interact with the [Open AI API](https://beta.openai.com/docs/api-reference/introduction). If you or your business relies on this package, it's important to support the developers who have contributed their time and effort to create and maintain this valuable tool:
+**OpenAI PHP** for Laravel is a community-maintained PHP API client that allows you to interact with the [Open AI API](https://platform.openai.com/docs/api-reference/introduction). If you or your business relies on this package, it's important to support the developers who have contributed their time and effort to create and maintain this valuable tool:
 
 - Nuno Maduro: **[github.com/sponsors/nunomaduro](https://github.com/sponsors/nunomaduro)**
 - Sandro Gehri: **[github.com/sponsors/gehrisandro](https://github.com/sponsors/gehrisandro)**