fix #11211 (CR 602.3)

(Golgothian Sylex and Apocalypse Chime)

Mage/src/main/java/mage/filter/predicate/card/ExpansionSetPredicate.java

@@ -13,6 +13,10 @@ public class ExpansionSetPredicate implements Predicate<Card> {
 
     private final String setCode;
 
+    /**
+     * Per CR 206.1, the expansion symbol has no effect on game play.
+     * Use only for utility or silver-bordered / acorn mechanics.
+     */
     public ExpansionSetPredicate(String setCode) {
         this.setCode = setCode;
     }