This reverts commit 246216e599.
3.9.1 does not compile due to patch collision:
> applying patch /nix/store/sickncxw0s730j6gfrnlsi5ndgysi6la-libxml2-cmake-find-package.patch
> patching file CMakeLists.txt
> Hunk #1 FAILED at 42.
Fixing it is not trivial as upstream started bundling libxml2:
https://github.com/NixOS/nixpkgs/pull/182941#issuecomment-1195308936
Let's revert the update for now.