[PL/TH2M] Remove duplicate unused derivatives

Already stored in phase transition data and computed
by the corresponding models.

ProcessLib/TH2M/ConstitutiveRelations/ConstitutiveData.h

@@ -181,8 +181,6 @@ struct ConstitutiveTempData
     double drho_h_eff_dT = std::numeric_limits<double>::quiet_NaN();
     double drho_h_eff_dp_GR = std::numeric_limits<double>::quiet_NaN();
     double drho_h_eff_dp_cap = std::numeric_limits<double>::quiet_NaN();
-    double dh_G_dT = std::numeric_limits<double>::quiet_NaN();
-    double dh_L_dT = std::numeric_limits<double>::quiet_NaN();
     double dfC_4_MCpG_dp_GR = std::numeric_limits<double>::quiet_NaN();
     double dfC_4_MCpG_dT = std::numeric_limits<double>::quiet_NaN();
     double dfC_4_MCT_dT = std::numeric_limits<double>::quiet_NaN();