updates readme to indicate new min version of php

Author: gilzow

README.md

@@ -4,7 +4,7 @@
 
 This library provides a streamlined and easy to use way to interact with a Platform.sh environment.  It offers utility methods to access routes and relationships more cleanly than reading the raw environment variables yourself.
 
-This library requires PHP 7.2 or later.
+This library requires PHP 7.4 or later.
 
 ## Install