Patch positive value for test on ScaledKernel

Author: theogf

test/kernels/scaledkernel.jl

@@ -40,5 +40,5 @@
             @test_broken kerneldiagmatrix!(tmp_diag, ks, x) ≈ kerneldiagmatrix(ks, x)
         end
     end
-    test_ADs(x->x[1] * SqExponentialKernel(), rand(1))
+    test_ADs(x->exp(x[1]) * SqExponentialKernel(), rand(1))
 end