define insorted rules in 1.6 only

Author: Miha Zgubic

src/rulesets/Base/nondiff.jl

@@ -41,8 +41,8 @@
 @non_differentiable getindex(::AbstractArray{Bool}, ::Any...)
 @non_differentiable hcat(::AbstractArray{Bool}...)
 @non_differentiable hvcat(::Any, ::AbstractArray{Bool}...)
-@non_differentiable insorted(::Any, ::AbstractVector)
-@non_differentiable insorted(::Any, ::AbstractRange)
+VERSION >= v"1.6" && @non_differentiable insorted(::Any, ::AbstractVector)
+VERSION >= v"1.6" && @non_differentiable insorted(::Any, ::AbstractRange)
 @non_differentiable isperm(::AbstractArray{Bool})
 @non_differentiable invperm(::AbstractArray{Bool})
 @non_differentiable invpermute!(::Any, ::AbstractArray{Bool})