MEX files: no longer use “virtual” keyword when overriding a method

Automatically detected by clang-tidy with modernize-use-override check.

mex/sources/k_order_welfare/objective_m.hh

 /*
- * Copyright © 2021 Dynare Team
+ * Copyright © 2021-2023 Dynare Team
  *
  * This file is part of Dynare.
  *
@@ -37,7 +37,6 @@ private:
 
 public:
   explicit ObjectiveMFile(const std::string& modName, int ntt_arg);
-  virtual ~ObjectiveMFile() = default;
   void eval(const Vector& y, const Vector& x, const Vector& params, Vector& residual,
             std::vector<TwoDMatrix>& md) override;
 };

mex/sources/libkorder/dynamic_dll.hh

@@ -101,7 +101,7 @@ private:
 public:
   // construct and load Dynamic model DLL
   explicit DynamicModelDLL(const std::string& fname, int ntt_arg, int order);
-  virtual ~DynamicModelDLL();
+  ~DynamicModelDLL() override;
 
   void eval(const Vector& y, const Vector& x, const Vector& params, const Vector& ySteady,
             Vector& residual, std::vector<TwoDMatrix>& md) override;

mex/sources/libkorder/dynamic_m.hh

 /*
- * Copyright © 2010-2022 Dynare Team
+ * Copyright © 2010-2023 Dynare Team
  *
  * This file is part of Dynare.
  *
@@ -45,7 +45,6 @@ private:
 
 public:
   explicit DynamicModelMFile(const std::string& modName, int ntt_arg);
-  virtual ~DynamicModelMFile() = default;
   void eval(const Vector& y, const Vector& x, const Vector& params, const Vector& ySteady,
             Vector& residual, std::vector<TwoDMatrix>& md) override;
 };

mex/sources/perfect_foresight_problem/DynamicModelCaller.hh

@@ -80,7 +80,6 @@ public:
   DynamicModelDllCaller(size_t ntt, mwIndex ny, mwIndex nx, const double* params_arg,
                         const double* steady_state_arg, const int32_T* g1_sparse_colptr_arg,
                         bool linear_arg, bool compute_jacobian_arg);
-  virtual ~DynamicModelDllCaller() = default;
   [[nodiscard]] double*
   y() override
   {