update php compat in readme

Author: dannyvankooten

readme.txt

@@ -55,7 +55,7 @@ This plugins helps you grow your email list in Mailchimp. You can use it to crea
 
 - Developer friendly. For some inspiration, check out our [repository of example code snippets](https://github.com/ibericode/mailchimp-for-wordpress/tree/main/sample-code-snippets).
 
-- Ready for PHP 8.4, but backwards-compatible all the way down to PHP 7.4.
+- Ready for PHP 8.5, but backwards-compatible all the way down to PHP 7.4.
 
 #### What is Mailchimp?