Skip Mooncake on 1.12 (#2705)

1.12 isn't being tested right now on Turing, so this doesn't actually
affect anything here; but DynamicPPL's integration test uses 1.12 and it
seems unfair to pin that to 1.11 when most of Turing's test suite should
pass on 1.12.

Author: penelopeysm

test/ad.jl

@@ -10,10 +10,8 @@ using Test
 using ..Models: gdemo_default
 import ForwardDiff, ReverseDiff
 
-# Detect if prerelease version, if so, we skip some tests
-const IS_PRERELEASE = !isempty(VERSION.prerelease)
-const INCLUDE_MOONCAKE = !IS_PRERELEASE
-
+# Skip Mooncake on 1.12 as it is not compatible yet
+const INCLUDE_MOONCAKE = VERSION >= v"1.12"
 if INCLUDE_MOONCAKE
     import Pkg
     Pkg.add("Mooncake")