Update doctest version guard (1.2 -> 1.4)

And add the same to docs/make.jl

Author: janEbert

docs/make.jl

@@ -2,7 +2,7 @@ using Documenter, Flux, NNlib
 
 DocMeta.setdocmeta!(Flux, :DocTestSetup, :(using Flux); recursive=true)
 makedocs(modules=[Flux, NNlib],
-         doctest = true,
+         doctest = VERSION >= v"1.4",
          sitename = "Flux",
          pages = ["Home" => "index.md",
                   "Building Models" =>

test/runtests.jl

@@ -41,7 +41,7 @@ Random.seed!(0)
   end
 
   @testset "Docs" begin
-    if VERSION >= v"1.2"
+    if VERSION >= v"1.4"
       DocMeta.setdocmeta!(Flux, :DocTestSetup, :(using Flux); recursive=true)
       doctest(Flux)
     end