message: remove usless forward declaration.
diff: #include <ringmesh/mesh/geogram_mesh.h>
  #include <ringmesh/mesh/mesh_builder.h>
  -namespace RINGMesh {
  - class GeoModel;
  -}
  -
  namespace RINGMesh {
  #define COMMON_GEOGRAM_MESH_BUILDER_IMPLEMENTATION( Class ) \
  