doc: minor modification in jldoctest

Author: franckgaga

src/plot_sim.jl

@@ -45,7 +45,7 @@ julia> model = LinModel(tf(1, [1, 1]), 1.0);
 
 julia> N = 5; U_data = fill(1.0, 1, N); Y_data = zeros(1, N);
 
-julia> for i=1:N; updatestate!(model, U_data[:, i]); Y_data[:, i] = model(); end; Y_data
+julia> foreach(i->(updatestate!(model, U_data[:, i]); Y_data[:, i] = model()), 1:N); Y_data
 1×5 Matrix{Float64}:
  0.632121  0.864665  0.950213  0.981684  0.993262