hephaestus: don't need opencl

Flake lock file updates:

• Updated input 'nixos-hardware':
    'github:NixOS/nixos-hardware/0cab18a48de7914ef8cad35dca0bb36868f3e1af' (2022-06-01)
  → 'github:NixOS/nixos-hardware/adcfd6aa860d1d129055039696bc457af7d50d0e' (2023-09-28)

flake.lock

@@ -80,11 +80,11 @@
     },
     "nixos-hardware": {
       "locked": {
-        "lastModified": 1654057797,
-        "narHash": "sha256-mXo7C4v7Jj2feBzcReu1Eu/3Rnw5b023E9kOyFsHZQw=",
+        "lastModified": 1695887975,
+        "narHash": "sha256-u3+5FR12dI305jCMb0fJNQx2qwoQ54lv1tPoEWp0hmg=",
         "owner": "NixOS",
         "repo": "nixos-hardware",
-        "rev": "0cab18a48de7914ef8cad35dca0bb36868f3e1af",
+        "rev": "adcfd6aa860d1d129055039696bc457af7d50d0e",
         "type": "github"
       },
       "original": {

hosts/hephaestus/default.nix

@@ -14,6 +14,8 @@
     ./secrets.nix
   ];
 
+  hardware.amdgpu.opencl = false;
+
   boot.kernelPackages = pkgs.linuxPackages;
 
   # Use the systemd-boot EFI boot loader.