test: removed picky Luenberger unit test

Author: franckgaga

test/test_state_estim.jl

@@ -230,7 +230,6 @@ end
     @test_throws ErrorException Luenberger(linmodel1, p̂=[0.5])
     @test_throws ErrorException Luenberger(linmodel1, p̂=fill(1.5, lo1.nx̂))
     @test_throws ErrorException Luenberger(LinModel(tf(1,[1, 0]),0.1), p̂=[0.5,0.6])
-    @test_throws ErrorException Luenberger(linmodel1, p̂=[0,0,0,0])
 end
 
 @testset "Luenberger estimator methods" begin