Update math.jl

Author: ValentinKaisermayer

test/Blocks/math.jl

@@ -1,5 +1,5 @@
 using ModelingToolkitStandardLibrary.Blocks
-using ModelingToolkit, OrdinaryDiffEq, Plots, Test
+using ModelingToolkit, OrdinaryDiffEq, Test
 using ModelingToolkitStandardLibrary.Blocks: _clamp, _dead_zone
 using ModelingToolkit: inputs, unbound_inputs, bound_inputs
 
@@ -269,4 +269,4 @@ end
     @test all(map(u->u in Set([b.input1.u, b.input2.u, int.input.u]), inputs(sys)))
     @test sol.retcode == :Success
     @test sol[int.input.u] ≈ atan.(sol[c1.output.u], sol[c2.output.u])
-end
+end