Remove useless "virtual" keyword in various ExprNode methods

src/ExprNode.hh

@@ -960,7 +960,7 @@ public:
   static double eval_opcode(double v1, BinaryOpcode op_code, double v2, int derivOrder) noexcept(false);
   double eval(const eval_context_t &eval_context) const noexcept(false) override;
   void compile(ostream &CompileCode, unsigned int &instruction_number, bool lhs_rhs, const temporary_terms_t &temporary_terms, const map_idx_t &map_idx, bool dynamic, bool steady_dynamic, const deriv_node_temp_terms_t &tef_terms) const override;
-  virtual expr_t Compute_RHS(expr_t arg1, expr_t arg2, int op, int op_type) const;
+  expr_t Compute_RHS(expr_t arg1, expr_t arg2, int op, int op_type) const;
   //! Returns first operand
   expr_t
   get_arg1() const
@@ -1065,7 +1065,7 @@ public:
   //! Substitute auxiliary variables by their expression in static model
   expr_t substituteStaticAuxiliaryVariable() const override;
   //! Substitute auxiliary variables by their expression in static model auxiliary variable definition
-  virtual expr_t substituteStaticAuxiliaryDefinition() const;
+  expr_t substituteStaticAuxiliaryDefinition() const;
 };
 
 //! Trinary operator node
@@ -1278,7 +1278,7 @@ public:
   bool containsExogenous() const override;
   int countDiffs() const override;
   bool isVariableNodeEqualTo(SymbolType type_arg, int variable_id, int lag_arg) const override;
-  virtual void writePrhs(ostream &output, ExprNodeOutputType output_type, const temporary_terms_t &temporary_terms, const temporary_terms_idxs_t &temporary_terms_idxs, const deriv_node_temp_terms_t &tef_terms, const string &ending) const;
+  void writePrhs(ostream &output, ExprNodeOutputType output_type, const temporary_terms_t &temporary_terms, const temporary_terms_idxs_t &temporary_terms_idxs, const deriv_node_temp_terms_t &tef_terms, const string &ending) const;
   expr_t replaceTrendVar() const override;
   expr_t detrend(int symb_id, bool log_trend, expr_t trend) const override;
   expr_t clone(DataTree &datatree) const override = 0;