fix: en_fleet alarm 11 modern orbiting method (#170)

Replace orbiting check with modern method to fix reported bug:
https://discord.com/channels/714022226810372107/1310348923482931230

Author: OH296

objects/obj_en_fleet/Alarm_11.gml

@@ -1,6 +1,5 @@
 
-if (action="") and (orbiting!=0){
-    orbiting=instance_nearest(x,y,obj_star);
+if (is_orbiting()){
     if (owner!=1) then orbiting.present_fleet[owner]+=1;
 }