update required php version in README

Author: pavog

README.md

@@ -7,7 +7,7 @@ The generated code can be found in `src/Api` and `src/Model`.
 It is recommended to use the wrappers in `src/Client` instead of the generated code.
 
 ## Requirements
-- PHP 8.2 or newer  
+- PHP 8.3 or newer  
 - PHP extensions: curl, json, mbstring  
 
 ## Installation