zfs: don't specify zfs arc cache

Turns out, zfs is smart!
ZFS already has sane defaults, no sense in limiting the size of the cache.

modules/zfs.nix

@@ -8,23 +8,7 @@
   boot.zfs.package = pkgs.zfs;
   boot.initrd.kernelModules = [ "zfs" ];
 
-  boot.kernelParams =
+  boot.kernelParams = [
-    let
-      # SEE: https://github.com/openzfs/zfs/pull/15437
-      # and https://blog.thalheim.io/2025/10/17/zfs-ate-my-ram-understanding-the-arc-cache/
-      arc_max_gb = (service_configs.gb_ram * 5) / 8;
-      arc_max_mb = arc_max_gb * 1000;
-      arc_max_kb = arc_max_mb * 1000;
-      arc_max_b = arc_max_kb * 1000;
-
-      arc_min_gb = 4;
-      arc_min_mb = arc_min_gb * 1000;
-      arc_min_kb = arc_min_mb * 1000;
-      arc_min_b = arc_min_kb * 1000;
-    in
-    [
-      "zfs.zfs_arc_max=${builtins.toString arc_max_b}"
-      "zfs.zfs_arc_min=${builtins.toString arc_min_b}"
     "zfs.zfs_txg_timeout=120" # longer TXG open time = larger sequential writes
   ];
 

service-configs.nix

@@ -7,7 +7,6 @@ rec {
   media_group = "media";
 
   cpu_arch = "znver3";
-  gb_ram = 64;
 
   ports = {
     # public