convert logging String.format to logging equivalent

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

@@ -59,7 +59,7 @@ public class Citygml3GeometryMapper extends GeometryWalker {
     public void visit(Polygon polygon) {
         parsePolygon(polygon.getId(), polygon.getExterior(), polygon.getInterior());
         if (polygon.getExterior() == null) {
-            logger.warn(String.format("No exterior: %s", polygon.getId()));
+            logger.warn("No exterior: {}", polygon.getId());
         }
     }