Fix identity test

Author: ChrisRackauckas

test/traits.jl

@@ -7,7 +7,7 @@ N = 4
 @testset "Traits" begin
     @test _isidentity_struct(I)
     @test _isidentity_struct(1.0 * I)
-    @test _isidentity_struct(SciMLBase.IdentityOperator{N}())
+    @test _isidentity_struct(SciMLBase.IdentityOperator(N))
     @test _isidentity_struct(SciMLBase.DiffEqIdentity(rand(4)))
     @test !_isidentity_struct(2.0 * I)
     @test !_isidentity_struct(rand(N, N))