fix polygon patches getting double added to geometry

CityDoctorParent/CityDoctorModel/src/main/java/de/hft/stuttgart/citydoctor2/mapper/citygml3/Citygml3GeometryMapper.java

@@ -111,7 +111,6 @@ public class Citygml3GeometryMapper extends GeometryWalker {
             conc.addInteriorRing(currentRing);
         }
         collection.addPatchMember(conc);
-        polygons.add(conc);
     }
 
     private void parsePolygon(String id, AbstractRingProperty exterior, List<AbstractRingProperty> interior) {