fix(nixos/alpha): work around game freezes

Seems like the new NVIDIA 560 driver causes games running through Proton to
eventually freeze. Downgrading for now.

nixos/hosts/alpha/hardware/default.nix

@@ -1,4 +1,5 @@
-{ pkgs
+{ config
+, pkgs
 , modulesPath
 , ...
 }: {
@@ -107,6 +108,14 @@
     nvidia = {
       # Must be set explicitly since https://github.com/NixOS/nixpkgs/commit/20c5d0adfb4cd7a06b7c1251cb0852f404d93e59
       open = false;
+      package = config.boot.kernelPackages.nvidiaPackages.mkDriver {
+        version = "555.58.02";
+        sha256_64bit = "sha256-xctt4TPRlOJ6r5S54h5W6PT6/3Zy2R4ASNFPu8TSHKM=";
+        sha256_aarch64 = "sha256-wb20isMrRg8PeQBU96lWJzBMkjfySAUaqt4EgZnhyF8=";
+        openSha256 = "sha256-8hyRiGB+m2hL3c9MDA/Pon+Xl6E788MZ50WrrAGUVuY=";
+        settingsSha256 = "sha256-ZpuVZybW6CFN/gz9rx+UJvQ715FZnAOYfHn5jt5Z2C8=";
+        persistencedSha256 = "sha256-a1D7ZZmcKFWfPjjH1REqPM5j/YLWKnbkP9qfRyIyxAw=";
+      };
       modesetting.enable = true;
       # Set up nvidia prime
       prime = {