[TH2M] Thermal conductivity is no longer a required property.

Now, thermal conductivity is a medium property, individual phase thermal conductivities are required only if in case of a mixing rule.

ProcessLib/TH2M/PhaseTransitionModels/PhaseTransitionModel.h

@@ -112,11 +112,9 @@ struct PhaseTransitionModel
 
         // check for minimum requirement definitions in media object
         std::array const required_gas_properties = {
-            MaterialPropertyLib::viscosity, MaterialPropertyLib::density,
-            MaterialPropertyLib::thermal_conductivity};
+            MaterialPropertyLib::viscosity, MaterialPropertyLib::density};
         std::array const required_liquid_properties = {
-            MaterialPropertyLib::viscosity, MaterialPropertyLib::density,
-            MaterialPropertyLib::thermal_conductivity};
+            MaterialPropertyLib::viscosity, MaterialPropertyLib::density};
 
         for (auto const& m : media)
         {