Update 2022-01-11-orm-2.11.md to be clear about some limitations over "Support for Readonly Properties"

source/blog/2022-01-11-orm-2.11.md

@@ -88,21 +88,25 @@ Another PHP 8.1 feature is the new readonly keyword that prevents the value of
 a property to be written again after it has been initialized in the constructor
 of an object.
 
-With ORM 2.11 the support now works as you would expect with no additional
-mapping options necessary:
+With ORM 2.11 the support now works only for entities which use the "NONE"
+strategy for identifier generator:
 
 ```php
 #[Entity, Table(name: 'author')]
 class Author
 {
-    #[Column, Id, GeneratedValue]
+    #[Column, Id, GeneratedValue(strategy: 'NONE')]
     private readonly int $id;
 
     #[Column]
     private readonly string $name;
 }
 ```
 
+For entities which use another strategy for their identifier generator,
+it will not work because when an entity is removed, the Unit of Work
+will try to set the value of the identifier as `null` which is not possible.
+
 ## AssociationOverrides and AttributeOverrides in Attribute Driver
 
 The new `AttributeDriver` for PHP 8 did not support the equivalent mapping