Fix the farmat error

Author: skywalker_cn

include/openmc/particle_data.h

@@ -400,10 +400,6 @@ class GeometryState {
   {
     return material_last_;
   }
-  const int& material_last() const
-  {
-    return material_last_;
-  }
 
   // temperature of current and last cell
   double& sqrtkT()
@@ -457,7 +453,6 @@ class GeometryState {
   double density_mult_ {1.0};      //!< density multiplier
   double density_mult_last_ {1.0}; //!< last density multiplier
 
-
 #ifdef OPENMC_DAGMC_ENABLED
   moab::DagMC::RayHistory history_;
   Direction last_dir_;