Added note about typed class constants in PDO extension

Author: jorgsowa

UPGRADING

@@ -140,12 +140,15 @@ PHP 8.4 UPGRADE NOTES
 9. Other Changes to Extensions
 ========================================
 
-- Spl:
+- PDO:
   . The class constants are typed now.
 
 - Reflection:
   . The class constants are typed now.
 
+- Spl:
+  . The class constants are typed now.
+
 ========================================
 10. New Global Constants
 ========================================