windows back to lts-18.13 temporarily

windows back to lts-18.13 temporarily

I can't seem to get stack to resolve dependencies with Win32-2.13.4.0,
no matter what I try. Why it blows up, I don't know.

And allow-newer: true actually causes it to downgrade Win32 to the one
version that won't build. Unbelivable that allows downgrades.

So just gonna have to wait for that to get into stackage nightly, and
then stack.yaml can be updated to use that, and the changes in this
commit reverted.