fix error

Author: simonbyrne

test/linalg/diagonal.jl

@@ -361,7 +361,7 @@ end
     Q = qrfact(randn(5, 5)).Q
     @test D * Q' == Array(D) * Q'
     Q = qrfact(randn(5, 5), Val(true)).Q
-    @test_throws MethodError mul2!(Q, D)
+    @test_throws ArgumentError mul2!(Q, D)
 end
 
 @testset "block diagonal matrices" begin