[Cache] Mention the changes in prefix_seed

Author: javiereguiluz

reference/configuration/framework.rst

@@ -2716,6 +2716,12 @@ It's also useful when using `blue/green deployment`_ strategies and more
 generally, when you need to abstract out the actual deployment directory (for
 example, when warming caches offline).
 
+.. versionadded:: 5.2
+
+    Starting from Symfony 5.2, the ``%kernel.container_class%`` parameter is no
+    longer appended automatically to the value of this option. This allows
+    sharing caches between applications or different environments.
+
 .. _reference-lock:
 
 lock