Simplify tests for new sortexp() method (#638)

Author: michikawa07

test/runtests.jl

@@ -1908,12 +1908,12 @@ end
 end
 
 @testset "Output ordered by unit exponent" begin
-    ordered = Unitful.sortexp(typeof(u"J*mol^-1*K^-1").parameters[1])
+    ordered = Unitful.sortexp(u"J*mol^-1*K^-1")
     @test typeof(ordered[1]) <: Unitful.Unit{:Joule,<:Any}
     @test typeof(ordered[2]) <: Unitful.Unit{:Kelvin,<:Any}
     @test typeof(ordered[3]) <: Unitful.Unit{:Mole,<:Any}
 
-    ordered = Unitful.sortexp(typeof(u"mol*J^-1*K^-1").parameters[1])
+    ordered = Unitful.sortexp(u"mol*J^-1*K^-1")
     @test typeof(ordered[1]) <: Unitful.Unit{:Mole,<:Any}
     @test typeof(ordered[2]) <: Unitful.Unit{:Joule,<:Any}
     @test typeof(ordered[3]) <: Unitful.Unit{:Kelvin,<:Any}