Remove unused parameter (Output)

src/artis-star/common/observer/Output.hpp

@@ -67,7 +67,7 @@ struct TimedIterator
   double _begin;
   double _step;
 
-  double begin(const std::vector <DiscreteTimeIterator<Time>> &its) const
+  double begin(const std::vector <DiscreteTimeIterator<Time>> & /* its */) const
   { return _begin; }
 
   iterator_type build(const typename View<Time>::Values &view) const