system(home): Disable nixpkgs release check

Necessary since we take advantage of newer hypridle and hyprlock
modules while sticking with an older version of nixpkgs to avoid issues
with newer versions of hyprland and ironbar.

Breakage may have been influenced by a dependency but seems to occur
with various combinations of hyprland and ironbar.

- hyprland v0.39.1 + ironbar v0.14.1
- hyprland v0.39.1 + ironbar master
- hyprland master + ironbar master

modules/system.nix

@@ -134,6 +134,8 @@ in
       sharedModules = singleton {
         home = {
           inherit (cfg) stateVersion;
+
+          enableNixpkgsReleaseCheck = false;
         };
 
         programs.man.generateCaches = true;