Add missing 'override' keyword

dune/gfe/densities/duneelasticitydensity.hh

@@ -73,7 +73,7 @@ namespace Dune::GFE
     }
 
     // Construct a copy of this density but using 'adouble' as the number type
-    virtual std::unique_ptr<LocalDensity<ElementOrIntersection,ATargetSpace> > makeActiveDensity() const
+    virtual std::unique_ptr<LocalDensity<ElementOrIntersection,ATargetSpace> > makeActiveDensity() const override
     {
       // The active dune-elasticity density
       auto activeDensity = elasticityDensity_->makeActiveDensity();