Remove unix-2.8 patching for now
I originally patched these libraries in anticipation of GHC HEAD bundling the yet-to-be-released `unix-2.8` instead of `unix-2.7`. However, since then HEAD has switched back to `unix-2.7` and doesn't show any signs of going back to `2.8` any time soon. Keeping these patches around, therefore, is a bit wasteful since it results in more `Cabal` store cache misses without any benefits, since these libraries build on HEAD just fine. Until the need to actually adjust to `unix-2.8` arises once more, I'm going to remove these patches for now.