replace groovy code with ability in card script

release/Magarena/scripts/Beetleback_Chief.groovy

@@ -1,21 +0,0 @@
-[
-    new MagicWhenComesIntoPlayTrigger() {
-        @Override
-        public MagicEvent executeTrigger(final MagicGame game, final MagicPermanent permanent, final MagicPayedCost payedCost) {
-            return new MagicEvent(
-                permanent,
-                this,
-                "PN puts two 1/1 red Goblin creature tokens onto the battlefield."
-            );
-        }
-
-        @Override
-        public void executeEvent(final MagicGame game, final MagicEvent event) {
-            game.doAction(new MagicPlayTokensAction(
-                event.getPlayer(),
-                TokenCardDefinitions.get("Goblin1"),
-                2
-            ));
-        }
-    }
-]

release/Magarena/scripts/Beetleback_Chief.txt

@@ -7,5 +7,5 @@ type=Creature
 subtype=Goblin,Warrior
 cost={2}{R}{R}
 pt=2/2
+ability=enters effect PN puts two 1/1 red Goblin creature tokens onto the battlefield.
 timing=main
-requires_groovy_code