message: remove mat from include
diff: #include <stan/services/experimental/advi/fullrank.hpp>
  #include <stan/services/experimental/advi/meanfield.hpp>
  #include <stan/math/opencl/opencl_context.hpp>
  -#include <stan/math/prim/mat/fun/Eigen.hpp>
  +#include <stan/math/prim/fun/Eigen.hpp>
  #include <boost/date_time/posix_time/posix_time_types.hpp>
  #include <fstream>
  #include <sstream>
  