Flip version gate to VERSION < v"1.6" for the fold workaround

Puts the old-Julia workaround in the leading branch so it can be dropped
easily once Julia 1.0 support is no longer needed.

Created by generative AI.

Author: oschulz

src/with_ladj.jl

@@ -143,12 +143,7 @@ function _with_ladj_on_mapped(y_with_ladj::Tuple{NoLogAbsDetJacobian, Vararg{Uni
     return first(y_with_ladj)
 end
 
-@static if VERSION >= v"1.6"
-    function _with_ladj_on_mapped(y_with_ladj::Tuple{Tuple{Any,Real}, Vararg{Union{NoLogAbsDetJacobian, Tuple{Any,Real}}}})
-        a, bs = first(y_with_ladj), Base.tail(y_with_ladj)
-        return foldl(_combine_y_ladj, bs, init = ((a[1],), a[2]))
-    end
-else
+@static if VERSION < v"1.6"
     # Hand-rolled foldl, foldl over tuples is not inferrable on Julia < 1.6:
     _foldl_combine_y_ladj(acc) = acc
     _foldl_combine_y_ladj(acc, b, bs...) = _foldl_combine_y_ladj(_combine_y_ladj(acc, b), bs...)
@@ -157,6 +152,11 @@ else
         a = first(y_with_ladj)
         return _foldl_combine_y_ladj(((a[1],), a[2]), Base.tail(y_with_ladj)...)
     end
+else
+    function _with_ladj_on_mapped(y_with_ladj::Tuple{Tuple{Any,Real}, Vararg{Union{NoLogAbsDetJacobian, Tuple{Any,Real}}}})
+        a, bs = first(y_with_ladj), Base.tail(y_with_ladj)
+        return foldl(_combine_y_ladj, bs, init = ((a[1],), a[2]))
+    end
 end
 
 @static if VERSION >= v"1.6"