Revert "zfs: kernel and user overlay to 2.1.7"

* Setting /sys/module/zfs/parameters/zfs_dmu_offset_next_sync to 1
  instead of overlay utilization
* Ref: openzfs/zfs/pull/12746

This reverts commit 02462d5.

flake.nix

@@ -62,12 +62,12 @@
     (
       let
         system = "x86_64-linux";
-        overlays = [(import ./overlay.nix inputs)];
+        # overlays = [(import ./overlay.nix inputs)];
       in
         bitte.lib.mkBitteStack {
           inherit inputs;
           inherit (inputs) self;
-          inherit overlays;
+          # inherit overlays;
           domain = "bitte.aws.iohkdev.io";
           bitteProfile = inputs.self.${system}.metal.bitteProfile.default;
           hydrationProfile = inputs.self.${system}.cloud.hydrationProfile.default;

nix/metal/bitteProfile/default.nix

@@ -75,18 +75,6 @@ in {
                   path = "/nix";
                   read_only = false;
                 };
-
-                boot.kernelPackages = pkgs.linuxPackages.extend (self: super: {
-                  zfs = super.zfs.overrideAttrs (old: {
-                    name = "zfs-kernel-2.1.7-${super.kernel.version}";
-                    src = pkgs.fetchFromGitHub {
-                      owner = "openzfs";
-                      repo = "zfs";
-                      rev = "zfs-2.1.7";
-                      sha256 = "sha256-vLm6RE11nqOCoYXne79JU3nUQnVEUNbwrULwFfghWcI=";
-                    };
-                  });
-                });
               });
           }
           // extraConfig;