[ci skip] Drop "Fix CME on adding a passenger in CreatureSpawnEvent" (#6384)

This is no longer needed as Entity#passengers is an ImmutableList as of 1.17

patches/server/Optimize-indirect-passenger-iteration.patch

@@ -13,7 +13,7 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
  
      private Stream<Entity> getIndirectPassengersStream() {
 +        if (this.passengers.isEmpty()) { return Stream.of(); } // Paper
-         return ImmutableList.copyOf(this.passengers).stream().flatMap(Entity::getSelfAndPassengers); // Paper
+         return this.passengers.stream().flatMap(Entity::getSelfAndPassengers);
      }
  
      @Override