Fix write_latex_dynamic_model(write_equation_tags) for ramsey_model

When using ramsey_model, the M_.ramsey_eq_nbr planner FOCs are written before the M_.orig_eq_nbr private sector FOCs for which the equation tags have been provided. But the equation tags are printed for the first M_.orig_eq_nbr equations, not for the M_.ramsey_eq_nbr+1:M_.eq_nbr ones.